Fix cache listing to include files from new structure

- Update list_all() to scan cache_dir for legacy files directly
  (old files stored as CACHE_DIR/{hash}, not CACHE_DIR/legacy/)
- Update cache listing endpoints to use cache_manager.list_all()
  instead of iterating CACHE_DIR.iterdir() directly
- This ensures uploaded files appear in the cache UI regardless
  of whether they're in the old or new cache structure

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

cache_manager.py

@@ -278,20 +278,39 @@ class L1CacheManager:
     def list_all(self) -> List[CachedFile]:
         """List all cached files."""
         files = []
+        seen_hashes = set()
+
+        # New cache structure entries
         for entry in self.cache.list_entries():
             files.append(CachedFile.from_cache_entry(entry))
+            if entry.content_hash:
+                seen_hashes.add(entry.content_hash)
 
-        # Include legacy files
-        for f in self.legacy_dir.iterdir():
-            if f.is_file():
-                files.append(CachedFile(
-                    node_id=f.name,
-                    content_hash=f.name,
-                    path=f,
-                    size_bytes=f.stat().st_size,
-                    node_type="legacy",
-                    created_at=f.stat().st_mtime,
-                ))
+        # Legacy files stored directly in cache_dir (old structure)
+        # These are files named by content_hash directly in CACHE_DIR
+        for f in self.cache_dir.iterdir():
+            # Skip directories and special files
+            if not f.is_file():
+                continue
+            # Skip metadata/auxiliary files
+            if f.suffix in ('.json', '.mp4'):
+                continue
+            # Skip if name doesn't look like a hash (64 hex chars)
+            if len(f.name) != 64 or not all(c in '0123456789abcdef' for c in f.name):
+                continue
+            # Skip if already seen via new cache
+            if f.name in seen_hashes:
+                continue
+
+            files.append(CachedFile(
+                node_id=f.name,
+                content_hash=f.name,
+                path=f,
+                size_bytes=f.stat().st_size,
+                node_type="legacy",
+                created_at=f.stat().st_mtime,
+            ))
+            seen_hashes.add(f.name)
 
         return files