Add IPFS CID support for asset lookup

- Upload endpoint returns both CID and content_hash
- Cache manager handles both SHA3-256 hashes and IPFS CIDs
- get_by_cid() fetches from IPFS if not cached locally
- Execute tasks support :cid in addition to :hash

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

app/services/cache_service.py

@@ -453,8 +453,8 @@ class CacheService:
         content: bytes,
         filename: str,
         actor_id: str,
-    ) -> Tuple[Optional[str], Optional[str]]:
-        """Upload content to cache. Returns (content_hash, error)."""
+    ) -> Tuple[Optional[str], Optional[str], Optional[str]]:
+        """Upload content to cache. Returns (content_hash, ipfs_cid, error)."""
         import tempfile
 
         try:
@@ -466,7 +466,7 @@ class CacheService:
             # Detect MIME type before moving file
             mime_type = get_mime_type(tmp_path)
 
-            # Store in cache
+            # Store in cache (also stores in IPFS)
             cached, ipfs_cid = self.cache.put(tmp_path, node_type="upload", move=True)
             content_hash = cached.content_hash
 
@@ -479,9 +479,9 @@ class CacheService:
                 filename=filename
             )
 
-            return content_hash, None
+            return content_hash, ipfs_cid, None
         except Exception as e:
-            return None, f"Upload failed: {e}"
+            return None, None, f"Upload failed: {e}"
 
     async def list_media(
         self,