discover: replace Force DL toggle with Any Quality placeholder (Phase 0)

Replace the misleading Force DL toggle on the Sync page Discover tab with
a disabled Any Quality toggle. Stop sending force_download_all from
discover sync so discover playlists run ownership analysis instead of
blindly re-downloading owned tracks.

Adds PLAN-download-quality-flags.md describing the full refactor plan.

PLAN-download-quality-flags.md

@@ -0,0 +1,123 @@
+# Plan: Download Quality Flags Refactor
+
+## Background
+
+The current `force_download_all` flag is misleadingly named. It does NOT lower
+quality requirements or "force download any quality". It only skips the library
+ownership check so every track is treated as missing and re-downloaded regardless
+of whether the user already owns it.
+
+This causes two distinct problems:
+
+1. The name implies quality-related behavior that doesn't exist.
+2. The discover sync tab currently sends `force_download_all: true`, which means
+   every discover playlist sync re-downloads tracks the user already owns.
+
+Additionally, users have expressed a real need for a per-batch quality override:
+their main library should stay strict (FLAC preferred, high bitrate) while
+rotating/ephemeral playlists (discover) should grab whatever is available for
+quantity over quality.
+
+Per-client fallback settings already exist (Soulseek quality profile
+`fallback_enabled`, Deezer/Tidal/Qobuz `allow_fallback` chains) but they are
+global all-or-nothing flags. There is no way today to say "relax quality just
+for this one batch".
+
+## Goals
+
+1. Rename `force_download_all` to reflect what it actually does (skip ownership
+   check / re-download owned).
+2. Stop discover sync from blindly re-downloading owned tracks.
+3. Add a new per-batch "Any Quality" flag that bypasses quality filtering for
+   that specific batch only, without touching the user's global quality
+   settings.
+
+## Non-Goals
+
+- No changes to the global per-client quality/fallback settings.
+- No changes to the matching engine scoring.
+- No changes to album consistency / MusicBrainz preflight logic.
+
+## Phase 0 (this PR): UI framework only
+
+Scope is tiny and safe to ship immediately.
+
+- Replace the "Force DL" toggle in the Sync page Discover tab with an "Any
+  Quality" toggle.
+- Leave the new toggle permanently disabled / greyed out for now.
+- Tooltip on the toggle reads something like "Coming soon: download any
+  available quality for this batch".
+- Remove the `force_download_all: true` body payload from the discover sync
+  path. Discover playlists will now always run ownership analysis.
+- No backend changes in this phase.
+
+Files touched:
+- `webui/static/discover.js` - replace toggle HTML, remove `forceDownload`
+  plumbing from `syncDiscoverPlaylistFromTab` / `_doSyncDiscoverPlaylist`.
+
+## Phase 1: Rename `force_download_all`
+
+Rename to `skip_ownership_check` (backend) and surface in the UI as
+"Re-download Owned" (or equivalent).
+
+- Backend: add new key `skip_ownership_check` everywhere the flag is used.
+  Accept both keys on inbound API payloads for one release (back-compat).
+- Frontend: rename the Wishlist / Downloads modal toggles, keep the same
+  default behavior (wishlists still skip the library check by default).
+- Update `helper.js` tooltip description to match the new name and behavior.
+
+Files touched:
+- `web_server.py` (lines ~15663, 24858, 25858, 26065, 29051, 29057, 29062,
+  29104, 29135, 33556, 33596)
+- `webui/static/downloads.js` (lines ~195, 598, 2152, 2155, 2195, 2436)
+- `webui/static/wishlist-tools.js` (line ~6347)
+- `webui/static/helper.js` (lines ~663)
+
+## Phase 2: Implement "Any Quality" per-batch override
+
+Introduce a new batch flag `any_quality` that, when set, bypasses quality
+filtering for that batch only.
+
+Backend behavior:
+- Add `any_quality` to the batch dict alongside `skip_ownership_check`.
+- For Soulseek: when `any_quality` is true, skip the call to
+  `soulseek_client.filter_results_by_quality_preference()` and pass ranked
+  candidates through unchanged.
+- For Deezer / Tidal / Qobuz: when `any_quality` is true, temporarily force
+  the candidate selection path to treat `allow_fallback=True` AND start from
+  the lowest quality tier so downloads succeed fastest.
+- The flag is per-batch only. Global quality profile / `allow_fallback`
+  settings remain untouched.
+
+Frontend behavior:
+- Enable the "Any Quality" toggle added in Phase 0.
+- Remove the "Coming soon" tooltip, replace with a real description.
+- Wire the toggle into the discover sync POST body as `any_quality: true`.
+- Consider exposing the same toggle on the Wishlist / Downloads modal.
+
+Files touched:
+- `web_server.py` - batch creation + candidate selection path
+- `core/soulseek_client.py` - accept override in filter call
+- `core/deezer_download_client.py`, `core/tidal_download_client.py`,
+  `core/qobuz_client.py` - accept per-request quality override
+- `webui/static/discover.js` - enable toggle, send flag
+- `webui/static/downloads.js` - add matching toggle on manual download
+  modals
+
+## Risks / Open Questions
+
+- Soulseek quality profile bypass: is it safe to pass all density-filtered
+  candidates through without the priority filter? Likely yes, since the
+  matching engine already ranks by confidence and peer quality.
+- Streaming clients with strict API quality params (Tidal HiRes vs Lossless
+  entitlement, Qobuz subscription tiers): forcing lowest tier should be safe
+  for all users regardless of subscription.
+- Back-compat on the renamed flag: keep the old `force_download_all` key
+  accepted for at least one release cycle to avoid breaking any third-party
+  callers or stale browser sessions.
+
+## Rollout
+
+- Phase 0 ships with this PR (UI framework + discover fix).
+- Phase 1 and Phase 2 can ship as separate PRs on dev.
+- No migrations required; all flags are request-scoped and batch-scoped.

webui/static/discover.js

@@ -9123,10 +9123,10 @@ function renderDiscoverSyncCard(playlist, container, sourceLabel) {
                     <span class="discover-sync-toggle-slider"></span>
                 </label>
             </div>
-            <div class="discover-sync-toggle-wrapper" title="${isEmpty ? '' : 'Skip quality filters and download any available source'}">
+            <div class="discover-sync-toggle-wrapper" title="Coming soon: download any available quality for this batch, even if it's below your global quality profile. Useful for rotating discover playlists where quantity matters more than quality.">
-                <label class="discover-sync-toggle-label">Force DL</label>
+                <label class="discover-sync-toggle-label" style="opacity:0.5">Any Quality</label>
-                <label class="discover-sync-toggle">
+                <label class="discover-sync-toggle" style="opacity:0.5;cursor:not-allowed">
-                    <input type="checkbox" id="discover-force-dl-${playlist.type}" ${isEmpty ? 'disabled' : ''}>
+                    <input type="checkbox" id="discover-any-quality-${playlist.type}" disabled>
                     <span class="discover-sync-toggle-slider"></span>
                 </label>
             </div>
@@ -9173,15 +9173,10 @@ async function toggleDiscoverAutoUpdate(playlistType, enabled) {
 const _discoverSyncQueue = [];
 let _discoverSyncRunning = false;
 
-async function syncDiscoverPlaylistFromTab(playlistType, playlistName, forceDownload) {
+async function syncDiscoverPlaylistFromTab(playlistType, playlistName) {
-    // Read force-download toggle if not explicitly passed
-    if (forceDownload === undefined) {
-        const fdToggle = document.getElementById(`discover-force-dl-${playlistType}`);
-        forceDownload = fdToggle ? fdToggle.checked : false;
-    }
     // Serialize sync operations to avoid concurrent backend contention
     return new Promise((resolve) => {
-        _discoverSyncQueue.push({ playlistType, playlistName, forceDownload, resolve });
+        _discoverSyncQueue.push({ playlistType, playlistName, resolve });
         _processDiscoverSyncQueue();
     });
 }
@@ -9189,9 +9184,9 @@ async function syncDiscoverPlaylistFromTab(playlistType, playlistName, forceDown
 async function _processDiscoverSyncQueue() {
     if (_discoverSyncRunning || _discoverSyncQueue.length === 0) return;
     _discoverSyncRunning = true;
-    const { playlistType, playlistName, forceDownload, resolve } = _discoverSyncQueue.shift();
+    const { playlistType, playlistName, resolve } = _discoverSyncQueue.shift();
     try {
-        await _doSyncDiscoverPlaylist(playlistType, playlistName, forceDownload);
+        await _doSyncDiscoverPlaylist(playlistType, playlistName);
     } finally {
         _discoverSyncRunning = false;
         resolve();
@@ -9199,7 +9194,7 @@ async function _processDiscoverSyncQueue() {
     }
 }
 
-async function _doSyncDiscoverPlaylist(playlistType, playlistName, forceDownload) {
+async function _doSyncDiscoverPlaylist(playlistType, playlistName) {
     const btn = document.getElementById(`discover-sync-btn-${playlistType}`);
     if (btn) {
         btn.disabled = true;
@@ -9253,7 +9248,6 @@ async function _doSyncDiscoverPlaylist(playlistType, playlistName, forceDownload
             tracks: syncTracks,
             playlist_name: playlistName
         };
-        if (forceDownload) bodyPayload.force_download_all = true;
 
         const batchResponse = await fetch(`/api/playlists/${virtualPlaylistId}/start-missing-process`, {
             method: 'POST',
@@ -9263,8 +9257,7 @@ async function _doSyncDiscoverPlaylist(playlistType, playlistName, forceDownload
 
         const result = await batchResponse.json();
         if (result.success) {
-            const forceLabel = forceDownload ? ' (force download)' : '';
+            showToast(`Downloading ${playlistName} (${syncTracks.length} tracks)...`, 'info');
-            showToast(`Downloading ${playlistName}${forceLabel} (${syncTracks.length} tracks)...`, 'info');
             const card = document.getElementById(`discover-sync-card-${playlistType}`);
             if (card) {
                 const statusEl = card.querySelector('.discover-sync-status');

webui/static/sync-services.js

@@ -2777,7 +2777,7 @@ function _applySyncTabAction() {
             }
         }
         if (action.autoSync) {
-            syncDiscoverPlaylistFromTab(action.autoSync, action.autoSyncName || action.autoSync, action.forceDownload);
+            syncDiscoverPlaylistFromTab(action.autoSync, action.autoSyncName || action.autoSync);
         }
     };
     // Small delay to let lazy tab content render