fix(ui): remove per-source 'Allow quality fallback' checkboxes

Quality fallback is now a global setting in the Quality Profile
(ranked targets + fallback_enabled). The per-source allow_fallback
checkboxes on Tidal, Qobuz, HiFi, Deezer and Amazon were misleading —
they implied quality is still controlled per-source. Removed from HTML
and settings.js read/save. Backend defaults to allow_fallback=True
which is the correct behaviour.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

webui/index.html

@@ -4743,13 +4743,6 @@
                                         <div class="setting-help-text">
                                             Quality is set globally in <strong>Quality Profile</strong> (ranked targets) — Tidal fetches the highest tier your profile accepts.
                                         </div>
-                                        <label class="checkbox-inline" style="margin-top: 8px;">
-                                            <input type="checkbox" id="tidal-allow-fallback" checked>
-                                            Allow quality fallback
-                                        </label>
-                                        <div class="setting-help-text">
-                                            When disabled, only downloads at the exact derived quality. If unavailable, skips to the next source.
-                                        </div>
                                     </div>
                                     <div class="form-group">
                                         <label>Tidal Download Auth:</label>
@@ -4771,13 +4764,6 @@
                                         <div class="setting-help-text">
                                             Quality is set globally in <strong>Quality Profile</strong> (ranked targets) — Qobuz fetches the highest tier your profile accepts. Hi-Res requires a Qobuz Studio or Sublime subscription.
                                         </div>
-                                        <label class="checkbox-inline" style="margin-top: 8px;">
-                                            <input type="checkbox" id="qobuz-allow-fallback" checked>
-                                            Allow quality fallback
-                                        </label>
-                                        <div class="setting-help-text">
-                                            When disabled, only downloads at the exact quality selected. If unavailable, skips to the next source.
-                                        </div>
                                     </div>
                                     <div class="form-group">
                                         <label>Qobuz Account:</label>
@@ -4831,13 +4817,6 @@
                                         <div class="setting-help-text">
                                             Quality is set globally in <strong>Quality Profile</strong> (ranked targets) — HiFi fetches the highest tier your profile accepts. Uses public API instances — no account required.
                                         </div>
-                                        <label class="checkbox-inline" style="margin-top: 8px;">
-                                            <input type="checkbox" id="hifi-allow-fallback" checked>
-                                            Allow quality fallback
-                                        </label>
-                                        <div class="setting-help-text">
-                                            When disabled, only downloads at the exact quality selected. If unavailable, skips to the next source.
-                                        </div>
                                     </div>
                                     <div class="form-group">
                                         <label>HiFi Status:</label>
@@ -4873,13 +4852,6 @@
                                         <div class="setting-help-text">
                                             Quality is set globally in <strong>Quality Profile</strong> (ranked targets) — Deezer fetches the highest tier your profile accepts. FLAC requires a Deezer HiFi subscription.
                                         </div>
-                                        <label class="checkbox-inline" style="margin-top: 8px;">
-                                            <input type="checkbox" id="deezer-allow-fallback" checked>
-                                            Allow quality fallback
-                                        </label>
-                                        <div class="setting-help-text">
-                                            When disabled, only downloads at the exact quality selected. If unavailable, skips to the next source.
-                                        </div>
                                     </div>
                                     <div class="form-group">
                                         <label>Deezer ARL Token:</label>
@@ -4909,13 +4881,6 @@
                                         <div class="setting-help-text">
                                             Quality is set globally in <strong>Quality Profile</strong> (ranked targets) — Amazon fetches FLAC (24-bit/48kHz Hi-Res) when your profile wants lossless, otherwise a lossy tier. Downloads via T2Tunes proxy.
                                         </div>
-                                        <label class="checkbox-inline" style="margin-top: 8px;">
-                                            <input type="checkbox" id="amazon-allow-fallback" checked>
-                                            Allow quality fallback
-                                        </label>
-                                        <div class="setting-help-text">
-                                            Fall back to the next codec tier if the preferred one is unavailable.
-                                        </div>
                                     </div>
                                     <div class="form-group">
                                         <label>Connection:</label>

webui/static/settings.js

@@ -1155,13 +1155,8 @@ async function loadSettingsData() {
         loadArtSourceOrder(settings);
         // Per-source download quality is now derived from the global Quality
         // Profile (ranked targets) — the per-source quality selects were removed.
-        document.getElementById('tidal-allow-fallback').checked = settings.tidal_download?.allow_fallback !== false;
-        document.getElementById('qobuz-allow-fallback').checked = settings.qobuz?.allow_fallback !== false;
-        document.getElementById('hifi-allow-fallback').checked = settings.hifi_download?.allow_fallback !== false;
         loadHiFiInstances();
-        document.getElementById('deezer-allow-fallback').checked = settings.deezer_download?.allow_fallback !== false;
         document.getElementById('deezer-download-arl').value = settings.deezer_download?.arl || '';
-        document.getElementById('amazon-allow-fallback').checked = settings.amazon_download?.allow_fallback !== false;
         document.getElementById('lidarr-url').value = settings.lidarr_download?.url || '';
         document.getElementById('lidarr-api-key').value = settings.lidarr_download?.api_key || '';
         const _prowUrl = document.getElementById('prowlarr-url');
@@ -2978,11 +2973,10 @@ async function saveSettings(quiet = false) {
             usenet_download_path: document.getElementById('usenet-download-path')?.value || '',
         },
         tidal_download: {
-            // quality derived from the global Quality Profile (ranked targets)
+            // quality derived from the global Quality Profile (ranked targets); allow_fallback always true
-            allow_fallback: document.getElementById('tidal-allow-fallback').checked,
         },
         hifi_download: {
-            allow_fallback: document.getElementById('hifi-allow-fallback').checked,
+            // quality derived from the global Quality Profile (ranked targets); allow_fallback always true
         },
         hifi: {
             embed_tags: document.getElementById('embed-hifi').checked,
@@ -2990,10 +2984,9 @@ async function saveSettings(quiet = false) {
         },
         deezer_download: {
             arl: document.getElementById('deezer-download-arl').value || '',
-            allow_fallback: document.getElementById('deezer-allow-fallback').checked,
         },
         amazon_download: {
-            allow_fallback: document.getElementById('amazon-allow-fallback').checked,
+            // quality derived from the global Quality Profile (ranked targets); allow_fallback always true
         },
         lidarr_download: {
             url: document.getElementById('lidarr-url').value || '',
@@ -3028,7 +3021,6 @@ async function saveSettings(quiet = false) {
         qobuz: {
             embed_tags: document.getElementById('embed-qobuz').checked,
             tags: _collectServiceTags('qobuz'),
-            allow_fallback: document.getElementById('qobuz-allow-fallback').checked,
         },
         database: {
             max_workers: parseInt(document.getElementById('max-workers').value)