feat(core): register sequence router in main.py

app/main.py

@@ -39,6 +39,7 @@ from app.routes import (
     workflows,
     currencies,
     taxes,
+    sequences,
 )
 
 
@@ -190,6 +191,7 @@ def create_app() -> FastAPI:
     app.include_router(workflows.router)
     app.include_router(currencies.router)
     app.include_router(taxes.router)
+    app.include_router(sequences.router)
 
     # ── Register plugin routes (before SPA catch-all) ────────────────
     registry = get_registry()