feat(bookshelf): add filter bar with HTMX integration and filter persistence

- Add bookshelf route with library selection from query param or first available
- Add filter bar UI with library selector, search, and filter controls
- Integrate HTMX for dynamic filtering (hx-get to /api/media-items/filtered)
- Add Alpine.js component for filter state management
- Add filter save/load functionality via /api/bookshelf/filters endpoint
- Update bookshelf.ts to use Alpine.js for reactive state instead of DOM manipulation

internal/router/frontend.go

@@ -203,6 +203,58 @@ func registerFrontendRoutes(cfg *Config) {
 		return c.HTML(http.StatusOK, buf.String())
 	})
 
+	// Bookshelf Page
+	frontendProtected.GET("/bookshelf", func(c *echo.Context) error {
+		user, err := getTemplateUserWithTheme(c, cfg)
+		if err != nil {
+			return renderErrorPage(c, "Error loading user", "user_load_error")
+		}
+
+		var errorMsg string
+
+		// Get library_id from query param or user's first library
+		libraryID := c.QueryParam("library_id")
+		if libraryID == "" {
+			userUUID, _ := uuid.Parse(user.ID)
+			libraries, err := cfg.Queries.GetUserVisibleLibraries(c.Request().Context(), uuidToPGType(userUUID))
+			if err == nil && len(libraries) > 0 {
+				libUUID, _ := uuid.FromBytes(libraries[0].ID.Bytes[0:16])
+				libraryID = libUUID.String()
+			} else {
+				errorMsg = "No libraries available"
+			}
+		}
+
+		// Get libraries for dropdown
+		userUUID, _ := uuid.Parse(user.ID)
+		libraries, err := cfg.Queries.GetUserVisibleLibraries(c.Request().Context(), uuidToPGType(userUUID))
+		if err != nil {
+			log.Printf("GetUserVisibleLibraries failed: %v", err)
+			libraries = []database.GetUserVisibleLibrariesRow{}
+			if errorMsg == "" {
+				errorMsg = "Error loading libraries"
+			}
+		}
+
+		libData := make([]templates.LibraryData, len(libraries))
+		for i, lib := range libraries {
+			libUUID, _ := uuid.FromBytes(lib.ID.Bytes[0:16])
+			libData[i] = templates.LibraryData{
+				ID:          libUUID.String(),
+				Name:        lib.Name,
+				Description: getText(lib.Description),
+				TypeName:    lib.TypeName,
+			}
+		}
+
+		var buf bytes.Buffer
+		err = templates.BookShelf(user, libData, libraryID, errorMsg).Render(c.Request().Context(), &buf)
+		if err != nil {
+			return err
+		}
+		return c.HTML(http.StatusOK, buf.String())
+	})
+
 	// Collections page
 	frontendProtected.GET("/collections", func(c *echo.Context) error {
 		user, err := getTemplateUserWithTheme(c, cfg)