feat(paths): abstract runtime path logic for frozen distribution packages (#969)

* feat(core): abstract runtime path logic for frozen distribution packages

* Address review feedback: revert browser MCP check, persistent data dir default when frozen, and add path tests

routes/embedding_routes.py

@@ -9,6 +9,7 @@ from pathlib import Path
 from fastapi import APIRouter, HTTPException, Form, Depends
 from core.constants import EMBEDDING_ENDPOINT_FILE, FASTEMBED_CACHE_DIR
 from core.middleware import require_admin
+from src.runtime_paths import get_app_root
 
 logger = logging.getLogger(__name__)