docs: Add godoc comments to exported functions

Add missing godoc comments to:
- NewRateLimiter and Allow in ratelimit.go
- SnapshotSyncStatus in temperature_proxy.go
- NewClient and GetVersion in pkg/pmg/client.go

internal/api/ratelimit.go

@@ -14,6 +14,8 @@ type RateLimiter struct {
 	stopCleanup chan struct{}
 }
 
+// NewRateLimiter creates a rate limiter that allows limit requests per window duration.
+// It starts a background goroutine to periodically clean up old entries.
 func NewRateLimiter(limit int, window time.Duration) *RateLimiter {
 	rl := &RateLimiter{
 		attempts:    make(map[string][]time.Time),
@@ -45,6 +47,8 @@ func (rl *RateLimiter) Stop() {
 	close(rl.stopCleanup)
 }
 
+// Allow checks if a request from the given IP address is within the rate limit.
+// Returns true if the request is allowed, false if the rate limit is exceeded.
 func (rl *RateLimiter) Allow(ip string) bool {
 	rl.mu.Lock()
 	defer rl.mu.Unlock()

internal/api/temperature_proxy.go

@@ -84,6 +84,7 @@ func (h *TemperatureProxyHandlers) recordSync(instance string, refreshSeconds in
 	}
 }
 
+// SnapshotSyncStatus returns a copy of the current sync status for all temperature proxies.
 func (h *TemperatureProxyHandlers) SnapshotSyncStatus() map[string]proxySyncState {
 	if h == nil {
 		return nil

pkg/pmg/client.go

@@ -126,6 +126,7 @@ type BackupEntry struct {
 	Timestamp flexibleInt `json:"timestamp"`
 }
 
+// NewClient creates a new PMG (Proxmox Mail Gateway) API client.
 func NewClient(cfg ClientConfig) (*Client, error) {
 	if cfg.Timeout <= 0 {
 		cfg.Timeout = 60 * time.Second
@@ -395,6 +396,7 @@ func (c *Client) getJSON(ctx context.Context, path string, params url.Values, ou
 	return nil
 }
 
+// GetVersion returns version information for the PMG instance.
 func (c *Client) GetVersion(ctx context.Context) (*VersionInfo, error) {
 	var resp apiResponse[VersionInfo]
 	if err := c.getJSON(ctx, "/version", nil, &resp); err != nil {