feat(reader): add reader JavaScript loading and backend support

- templates/reader.templ: add script tag to load main.js
- Enables reader shell and Alpine components to initialize
- internal/handlers/reader.go: add GetMediaReadingProgress handler
- Backend now supports fetching reading progress via API
- GET /api/media-items/:id/progress returns current progress

internal/handlers/reader.go

@@ -570,7 +570,7 @@ func (h *ReaderHandler) generatePDFThumbnail(fullPath string, page int, width, h
 	return []byte{}, nil
 }
 
-func (h *ReaderHandler) ParseEbook(c echo.Context) error {
+func (h *ReaderHandler) ParseEbook(c *echo.Context) error {
 	mediaItemID := c.Param("mediaItemId")
 	parsedUUID, err := uuid.Parse(mediaItemID)
 	if err != nil {