Add offline RefreshPrices, fix sync bugs, implement auto-restart

- Implement RefreshPrices for local-first mode
  - Update prices from local_components.current_price cache
  - Graceful degradation when component not found
  - Add PriceUpdatedAt timestamp to LocalConfiguration model
  - Support both authenticated and no-auth price refresh

- Fix sync duplicate entry bug
  - pushConfigurationUpdate now ensures server_id exists before update
  - Fetch from LocalConfiguration.ServerID or search on server if missing
  - Update local config with server_id after finding

- Add application auto-restart after settings save
  - Implement restartProcess() using syscall.Exec
  - Setup handler signals restart via channel
  - Setup page polls /health endpoint and redirects when ready
  - Add "Back" button on setup page when settings exist

- Fix setup handler password handling
  - Use PasswordEncrypted field consistently
  - Support empty password by using saved value

- Improve sync status handling
  - Add fallback for is_offline check in SyncStatusPartial
  - Enhance background sync logging with prefixes

- Update CLAUDE.md documentation
  - Mark Phase 2.5 tasks as complete
  - Add UI Improvements section with future tasks
  - Update SQLite tables documentation

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

internal/handlers/sync.go

@@ -285,20 +285,30 @@ func (h *SyncHandler) GetPendingChanges(c *gin.Context) {
 // SyncStatusPartial renders the sync status partial for htmx
 // GET /partials/sync-status
 func (h *SyncHandler) SyncStatusPartial(c *gin.Context) {
-	// Check online status
-	isOffline, _ := c.Get("is_offline")
+	// Check online status from middleware
+	isOfflineValue, exists := c.Get("is_offline")
+	isOffline := false
+	if exists {
+		isOffline = isOfflineValue.(bool)
+	} else {
+		// Fallback: check directly if middleware didn't set it
+		isOffline = !h.checkOnline()
+		slog.Warn("is_offline not found in context, checking directly")
+	}
 
 	// Get pending count
 	pendingCount := h.localDB.GetPendingCount()
 
+	slog.Debug("rendering sync status", "is_offline", isOffline, "pending_count", pendingCount)
+
 	data := gin.H{
-		"IsOffline":    isOffline.(bool),
+		"IsOffline":    isOffline,
 		"PendingCount": pendingCount,
 	}
 
 	c.Header("Content-Type", "text/html; charset=utf-8")
 	if err := h.tmpl.ExecuteTemplate(c.Writer, "sync_status", data); err != nil {
 		slog.Error("failed to render sync_status template", "error", err)
-		c.String(http.StatusInternalServerError, "Template error")
+		c.String(http.StatusInternalServerError, "Template error: "+err.Error())
 	}
 }