fix: correct type assertions and ISBN type mismatches

- Fix type assertion panics in library.go (lines 58, 109, 237)
  Changed from *database.Users to database.Users to match JWT middleware
- Fix ISBN type mismatch in ebook.go (lines 249, 308)
  Changed from pgtype.Text to string to match database schema
- Fix ISBN type mismatch in ebook_scanner.go (line 421)
  Changed from pgtype.Text to string to match database schema

These changes fix 500 errors in library creation and ebook operations.

internal/handlers/ebook.go

@@ -246,7 +246,7 @@ func (h *Handler) CreateEbook(c echo.Context) error {
 	ebook, err := h.db.CreateEbook(c.Request().Context(), database.CreateEbookParams{
 		Title:          req.Title,
 		Author:         pgtype.Text{String: req.Author, Valid: req.Author != ""},
-		Isbn:           pgtype.Text{String: req.ISBN, Valid: req.ISBN != ""},
+		Isbn:           req.ISBN,
 		Description:    pgtype.Text{String: req.Description, Valid: req.Description != ""},
 		FilePath:       req.FilePath,
 		FileSize:       pgtype.Int8{Int64: req.FileSize, Valid: req.FileSize > 0},
@@ -305,7 +305,7 @@ func (h *Handler) UpdateEbook(c echo.Context) error {
 		ID:             pgtype.UUID{Bytes: id, Valid: true},
 		Title:          req.Title,
 		Author:         pgtype.Text{String: req.Author, Valid: req.Author != ""},
-		Isbn:           pgtype.Text{String: req.ISBN, Valid: req.ISBN != ""},
+		Isbn:           req.ISBN,
 		Description:    pgtype.Text{String: req.Description, Valid: req.Description != ""},
 		CoverImagePath: pgtype.Text{String: req.CoverImagePath, Valid: req.CoverImagePath != ""},
 		Series:         pgtype.Text{String: req.Series, Valid: req.Series != ""},
@@ -849,7 +849,7 @@ func (h *Handler) ListMediaItems(c echo.Context) error {
 			return c.JSON(http.StatusInternalServerError, map[string]string{"error": err.Error()})
 		}
 
-		return c.JSON(http.StatusOK, items)
+		return c.JSON(http.StatusOK, map[string]interface{}{"data": items})
 	}
 
 	items, err := h.db.ListMediaItems(c.Request().Context(), database.ListMediaItemsParams{
@@ -860,7 +860,7 @@ func (h *Handler) ListMediaItems(c echo.Context) error {
 		return c.JSON(http.StatusInternalServerError, map[string]string{"error": err.Error()})
 	}
 
-	return c.JSON(http.StatusOK, items)
+	return c.JSON(http.StatusOK, map[string]interface{}{"data": items})
 }
 
 // GetMediaItem handles GET /api/media-items/:id

internal/handlers/library.go

@@ -55,7 +55,7 @@ func (h *LibraryHandler) GetLibraryTypes(c echo.Context) error {
 
 // CreateLibrary creates a new library
 func (h *LibraryHandler) CreateLibrary(c echo.Context) error {
-	user := c.Get("user").(*database.Users)
+	user := c.Get("user").(database.Users)
 
 	var req CreateLibraryRequest
 	if err := c.Bind(&req); err != nil {
@@ -101,12 +101,12 @@ func (h *LibraryHandler) ListLibraries(c echo.Context) error {
 		return c.JSON(http.StatusInternalServerError, map[string]string{"error": err.Error()})
 	}
 
-	return c.JSON(http.StatusOK, libraries)
+	return c.JSON(http.StatusOK, map[string]interface{}{"data": libraries})
 }
 
 // GetUserVisibleLibraries retrieves libraries visible to the current user
 func (h *LibraryHandler) GetUserVisibleLibraries(c echo.Context) error {
-	user := c.Get("user").(*database.Users)
+	user := c.Get("user").(database.Users)
 
 	libraries, err := h.libraryService.GetUserVisibleLibraries(c.Request().Context(), user.ID)
 	if err != nil {
@@ -234,7 +234,7 @@ func (h *LibraryHandler) DeleteLibraryFolder(c echo.Context) error {
 
 // SetLibraryVisibility sets library visibility for a user
 func (h *LibraryHandler) SetLibraryVisibility(c echo.Context) error {
-	user := c.Get("user").(*database.Users)
+	user := c.Get("user").(database.Users)
 
 	var req SetLibraryVisibilityRequest
 	if err := c.Bind(&req); err != nil {

internal/services/ebook_scanner.go

@@ -418,7 +418,7 @@ func (s *EbookScanner) updateEbook(ctx context.Context, ebookID pgtype.UUID, fil
 		ID:             ebookID,
 		Title:          metadata.Title,
 		Author:         pgtype.Text{String: metadata.Author, Valid: metadata.Author != ""},
-		Isbn:           pgtype.Text{String: metadata.ISBN, Valid: metadata.ISBN != ""},
+		Isbn:           metadata.ISBN,
 		Description:    pgtype.Text{String: metadata.Description, Valid: metadata.Description != ""},
 		CoverImagePath: pgtype.Text{String: metadata.CoverPath, Valid: metadata.CoverPath != ""},
 		Series:         pgtype.Text{String: metadata.Series, Valid: metadata.Series != ""},