fix: progress broadcasts now use correct WebSocket room names

- Fixed room name mismatch: ProgressService was broadcasting to
  'download_progress' but JS clients join 'downloads' room
- Added _get_room_for_progress_type() mapping function
- Updated all progress methods to use correct room names
- Added 13 new tests for room name mapping and broadcast verification
- Updated existing tests to expect correct room names
- Fixed JS clients to join valid rooms (downloads, queue, scan)

tests/integration/test_websocket_integration.py

@@ -325,8 +325,9 @@ class TestWebSocketScanIntegration:
         assert len(broadcasts) >= 2  # At least start and complete
 
         # Check for scan progress broadcasts
+        # Room name is 'scan' for SCAN type progress
         scan_broadcasts = [
-            b for b in broadcasts if b["room"] == "scan_progress"
+            b for b in broadcasts if b["room"] == "scan"
         ]
         assert len(scan_broadcasts) >= 2
 
@@ -379,8 +380,9 @@ class TestWebSocketScanIntegration:
             await anime_service.rescan()
 
         # Verify failure broadcast
+        # Room name is 'scan' for SCAN type progress
         scan_broadcasts = [
-            b for b in broadcasts if b["room"] == "scan_progress"
+            b for b in broadcasts if b["room"] == "scan"
         ]
         assert len(scan_broadcasts) >= 2  # Start and fail
 
@@ -438,7 +440,7 @@ class TestWebSocketProgressIntegration:
 
         start_broadcast = broadcasts[0]
         assert start_broadcast["data"]["status"] == "started"
-        assert start_broadcast["room"] == "download_progress"
+        assert start_broadcast["room"] == "downloads"  # Room name for DOWNLOAD type
 
         update_broadcast = broadcasts[1]
         assert update_broadcast["data"]["status"] == "in_progress"