feat(api): wire documents router and SQLite init in app factory

Why:
- App factory needs to mount document routes and initialize SQLite at startup

Changes:
- Import and mount documents_router
- Call init_db() on app creation

src/main.py

@@ -9,14 +9,18 @@ from src.core.exceptions import (
     chunking_exception_handler,
     benchmark_exception_handler,
 )
+from src.documents.routes import router as documents_router
+from src.storage.sqlite import init_db
 
 
 def create_app() -> FastAPI:
     """Create and configure the FastAPI application.
 
     Mounts domain routers and registers exception handlers.
-    Routers are imported lazily — domains are added in later phases.
     """
+    # Ensure SQLite tables exist at startup
+    init_db()
+
     app = FastAPI(
         title="RAG Chunking Benchmarker",
         description="Benchmark five chunking strategies on regulatory documents. "
@@ -37,6 +41,9 @@ def create_app() -> FastAPI:
     app.add_exception_handler(ChunkingError, chunking_exception_handler)
     app.add_exception_handler(BenchmarkError, benchmark_exception_handler)
 
+    # Mount domain routers
+    app.include_router(documents_router)
+
     return app