Add shareable search links and watched movie indicators

Share: "Copy Link" button generates a URL with ?s={history_id} that
loads the saved search results without auth. Recipients see the same
movie picks.

Watched: When viewing history results or shared searches, cards for
movies the logged-in user has since watched are dimmed with a green
"Watched" badge. Uses a new POST /api/library/watch-check endpoint.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

app/routers/mood.py

@@ -175,6 +175,29 @@ async def get_search_history(request: Request):
         await db.close()
 
 
+@router.get("/history/shared/{entry_id}")
+async def get_shared_history(entry_id: int):
+    """Public endpoint — returns a history entry by ID (no auth required)."""
+    db = await get_db()
+    try:
+        cursor = await db.execute(
+            "SELECT id, mood, results, meta, created_at FROM search_history WHERE id = ?",
+            (entry_id,),
+        )
+        row = await cursor.fetchone()
+        if not row:
+            raise HTTPException(status_code=404, detail="Search not found")
+        return {
+            "id": row["id"],
+            "mood": row["mood"],
+            "results": json.loads(row["results"]),
+            "meta": json.loads(row["meta"]) if row["meta"] else {},
+            "created_at": row["created_at"],
+        }
+    finally:
+        await db.close()
+
+
 @router.delete("/history/{entry_id}")
 async def delete_history_entry(entry_id: int, request: Request):
     user = await get_current_user(request)