Fix hidden library items not rendering in the browser

Items flagged hidden_from_guests (blacklisted tags) returned 404 for
<img> requests since tags cannot send the auth header. The API now
exposes signed raw_url/thumbnail_url fields (mirroring upload previews
and avatars), and the SPA uses them in the gallery, detail view,
duplicates and delete screens, and upload visual matches.

frontend/src/lib/types.ts

@@ -36,6 +36,7 @@ export interface DuplicateEntry {
   uploaded_by: string | null;
   e621_post_id: number | null;
   locations?: { id: number; rel_path: string }[];
+  thumbnail_url?: string;
   similarity?: number;
 }
 
@@ -126,6 +127,8 @@ export interface MediaItem {
   e621_post_id: number | null;
   e621_data: E621StoredPost | null;
   locations: MediaLocation[];
+  raw_url: string;
+  thumbnail_url: string;
   created_at: string;
   updated_at: string;
 }
@@ -209,7 +212,12 @@ export interface TempUpload {
   custom_notes: string;
   iqdb_data: E621IqdbCandidate[] | null;
   visual_matches:
-    | { j_id: string; filename: string; similarity: number }[]
+    | {
+        j_id: string;
+        filename: string;
+        similarity: number;
+        thumbnail_url?: string;
+      }[]
     | null;
   library_j_id: string | null;
   file_url: string | null;