Add SQLite project database + ComfyUI connector nodes

- db.py: ProjectDB class with SQLite schema (projects, data_files,
  sequences, history_trees), WAL mode, CRUD, import, and query helpers
- api_routes.py: REST API endpoints on NiceGUI/FastAPI for ComfyUI
  to query project data over the network
- project_loader.py: ComfyUI nodes (ProjectLoaderDynamic, Standard,
  VACE, LoRA) that fetch data from NiceGUI REST API via HTTP
- web/project_dynamic.js: Frontend JS for dynamic project loader node
- tab_projects_ng.py: Projects management tab in NiceGUI UI
- state.py: Added db, current_project, db_enabled fields
- main.py: DB init, API route registration, projects tab
- utils.py: sync_to_db() dual-write helper
- tab_batch_ng.py, tab_raw_ng.py, tab_timeline_ng.py: dual-write
  sync calls after save_json when project DB is enabled
- __init__.py: Merged project node class mappings
- tests/test_db.py: 30 tests for database layer
- tests/test_project_loader.py: 17 tests for ComfyUI connector nodes

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

utils.py

@@ -160,6 +160,43 @@ def get_file_mtime(path: str | Path) -> float:
         return path.stat().st_mtime
     return 0
 
+def sync_to_db(db, project_name: str, file_path: Path, data: dict) -> None:
+    """Dual-write helper: sync JSON data to the project database.
+
+    Resolves (or creates) the data_file, upserts all sequences from batch_data,
+    and saves the history_tree.
+    """
+    if not db or not project_name:
+        return
+    try:
+        proj = db.get_project(project_name)
+        if not proj:
+            return
+        file_name = Path(file_path).stem
+        df = db.get_data_file(proj["id"], file_name)
+        if not df:
+            top_level = {k: v for k, v in data.items()
+                         if k not in (KEY_BATCH_DATA, KEY_HISTORY_TREE)}
+            df_id = db.create_data_file(proj["id"], file_name, "generic", top_level)
+        else:
+            df_id = df["id"]
+
+        # Sync sequences
+        batch_data = data.get(KEY_BATCH_DATA, [])
+        if isinstance(batch_data, list):
+            db.delete_sequences_for_file(df_id)
+            for item in batch_data:
+                seq_num = int(item.get(KEY_SEQUENCE_NUMBER, 0))
+                db.upsert_sequence(df_id, seq_num, item)
+
+        # Sync history tree
+        history_tree = data.get(KEY_HISTORY_TREE)
+        if history_tree and isinstance(history_tree, dict):
+            db.save_history_tree(df_id, history_tree)
+    except Exception as e:
+        logger.warning(f"sync_to_db failed: {e}")
+
+
 def generate_templates(current_dir: Path) -> None:
     """Creates batch template files if folder is empty."""
     first = DEFAULTS.copy()