Add support for multiple images from Twitter links

- Fetch all images from Twitter syndication API (photos array)
- Store images with unified 'image' media type (first = thumbnail by ID order)
- Display multi-image tweets in grid layout on detail page
- Add hover cycling through images on home grid (2s interval)
- Show image count indicator on multi-image items
- Extract shared downloadAndStoreImages() helper for create/refresh
- Add migration to convert existing thumbnail/gallery types to image
- Make images clickable to open in new tab on detail page

internal/data/media/queries.go

@@ -9,7 +9,7 @@ import (
 type Row struct {
 	ID          int64
 	ItemID      int64
-	MediaType   string // 'original', 'thumbnail'
+	MediaType   string // 'original' (user uploads), 'image' (fetched from URLs)
 	ContentType string // MIME type
 	Data        []byte
 	Width       *int
@@ -68,13 +68,13 @@ func QFindByID(ctx context.Context, db *sql.DB, id int64) (*Row, error) {
 	return &row, nil
 }
 
-// QFindByItemID finds all media for an item.
+// QFindByItemID finds all media for an item, ordered by ID.
 func QFindByItemID(ctx context.Context, db *sql.DB, itemID int64) ([]Row, error) {
 	query := `
 		SELECT id, item_id, media_type, content_type, data, width, height, source_url, created_at
 		FROM media
 		WHERE item_id = $1
-		ORDER BY media_type ASC
+		ORDER BY id ASC
 	`
 
 	rows, err := db.QueryContext(ctx, query, itemID)
@@ -97,12 +97,13 @@ func QFindByItemID(ctx context.Context, db *sql.DB, itemID int64) ([]Row, error)
 	return media, rows.Err()
 }
 
-// QFindThumbnailByItemID finds the thumbnail for an item.
+// QFindThumbnailByItemID finds the first image for an item (used as thumbnail).
 func QFindThumbnailByItemID(ctx context.Context, db *sql.DB, itemID int64) (*Row, error) {
 	query := `
 		SELECT id, item_id, media_type, content_type, data, width, height, source_url, created_at
 		FROM media
-		WHERE item_id = $1 AND media_type = 'thumbnail'
+		WHERE item_id = $1 AND media_type = 'image'
+		ORDER BY id ASC
 		LIMIT 1
 	`