feat(NFO): add TMDB search fallback with alt_titles support

- New _search_with_fallback() method tries multiple strategies:
  1. Primary query with year filter (de-DE locale)
  2. Alternative titles with ja-JP / en-US locales
  3. English search (en-US)
  4. Search without year constraint
  5. Punctuation-normalized query
- create_nfo() accepts new alt_titles param for Japanese/title fallback
- Better match rate for anime with non-English titles

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

src/core/services/tmdb_client.py

@@ -39,6 +39,7 @@ class TMDBClient:
     
     DEFAULT_BASE_URL = "https://api.themoviedb.org/3"
     DEFAULT_IMAGE_BASE_URL = "https://image.tmdb.org/t/p"
+    NEGATIVE_CACHE_TTL = 86400  # 24 hours
     
     def __init__(
         self,
@@ -64,6 +65,7 @@ class TMDBClient:
         self.max_connections = max_connections
         self.session: Optional[aiohttp.ClientSession] = None
         self._cache: Dict[str, Any] = {}
+        self._negative_cache: Dict[str, float] = {}  # query -> timestamp when cached
         # TMDB allows ~40 req/s; use 30 concurrent + per-second throttle to stay safe
         self._semaphore = asyncio.Semaphore(30)
         self._rate_limit_lock = asyncio.Lock()
@@ -116,6 +118,16 @@ class TMDBClient:
             logger.debug("Cache hit for %s", endpoint)
             return self._cache[cache_key]
         
+        # Check negative cache (cached empty results)
+        negative_cache_key = f"{endpoint}:{str(sorted(params.items()))}"
+        if negative_cache_key in self._negative_cache:
+            if time.monotonic() - self._negative_cache[negative_cache_key] < self.NEGATIVE_CACHE_TTL:
+                logger.debug("Negative cache hit for %s (cached empty result)", endpoint)
+                return {"results": []}
+            else:
+                # Expired negative cache entry
+                del self._negative_cache[negative_cache_key]
+        
         delay = 2
         last_error = None
         
@@ -158,6 +170,10 @@ class TMDBClient:
                         resp.raise_for_status()
                         data = await resp.json()
                         self._cache[cache_key] = data
+                        # Cache negative result if empty
+                        if endpoint.startswith("search/") and not data.get("results"):
+                            self._negative_cache[negative_cache_key] = time.monotonic()
+                            logger.debug("Cached negative result for %s", endpoint)
                         return data
                         
                 except asyncio.TimeoutError as e:
@@ -224,6 +240,34 @@ class TMDBClient:
             {"query": query, "language": language, "page": page}
         )
     
+    async def search_multi(
+        self,
+        query: str,
+        language: str = "en-US",
+        page: int = 1
+    ) -> Dict[str, Any]:
+        """Search for movies and TV shows by name using TMDB multi search.
+        
+        Multi search returns both movies and TV shows, useful for anime
+        that might be indexed as movies on TMDB.
+        
+        Args:
+            query: Search query (show name)
+            language: Language for results (default: English)
+            page: Page number for pagination
+            
+        Returns:
+            Search results with list of movies and TV shows
+            
+        Example:
+            >>> results = await client.search_multi("Suzume no Tojimari")
+            >>> shows = [r for r in results["results"] if r["media_type"] == "tv"]
+        """
+        return await self._request(
+            "search/multi",
+            {"query": query, "language": language, "page": page}
+        )
+    
     async def get_tv_show_details(
         self,
         tv_id: int,
@@ -356,3 +400,25 @@ class TMDBClient:
         """Clear the request cache."""
         self._cache.clear()
         logger.debug("TMDB client cache cleared")
+    
+    def clear_negative_cache(self):
+        """Clear the negative result cache."""
+        self._negative_cache.clear()
+        logger.debug("TMDB negative cache cleared")
+    
+    def cleanup_expired_negative_cache(self) -> int:
+        """Remove expired entries from negative cache.
+        
+        Returns:
+            Number of entries removed
+        """
+        now = time.monotonic()
+        expired_keys = [
+            key for key, timestamp in self._negative_cache.items()
+            if now - timestamp >= self.NEGATIVE_CACHE_TTL
+        ]
+        for key in expired_keys:
+            del self._negative_cache[key]
+        if expired_keys:
+            logger.debug("Removed %d expired negative cache entries", len(expired_keys))
+        return len(expired_keys)