feat: migrate imphnen-backend-hackathon into workspace as imphnen-hackathon crate

Consolidates the standalone hackathon backend (16 crates) into a single
imphnen-hackathon crate following the existing clean architecture patterns.
All endpoints are exposed under /v1/hackathon/ via the gateway.

Features migrated:
- Auth: Supabase-based signup/login/GitHub OAuth/password reset (own JWT)
- Users: profile management with team listing
- Teams: CRUD with city validation, deadline enforcement, invite system
- Invitations: team member invitations with accept/reject flow
- Join Requests: team join request workflow
- Chat: team messaging with author/leader delete permissions
- Submissions: project submission lifecycle (draft→pending→submitted)
- Storage: Supabase Storage file upload endpoints
- Certificates: public user certificate data endpoint
- Winners: public winners listing
- Admin: admin-only CRUD for all entities

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

imphnen-gateway/src/lib.rs

@@ -16,6 +16,7 @@ use imphnen_dimentorin::{
     sessions_public_routes, sessions_protected_routes,
 };
 use imphnen_gacha::gacha_router;
+use imphnen_hackathon::{hackathon_router, HackathonConfig};
 use imphnen_iam::{
     auth_public_routes,
     permissions_protected_routes,
@@ -43,6 +44,7 @@ pub async fn gateway_service(
 
     let db = state.postgres_connection.conn.clone();
     let state_arc = Arc::new(state.clone());
+    let hackathon_config = Arc::new(HackathonConfig::from_env());
 
     let public_routes = Router::new()
         .merge(auth_public_routes(db.clone(), Arc::clone(&state_arc)).layer(from_fn(rate_limiting_middleware)))
@@ -65,6 +67,7 @@ pub async fn gateway_service(
     Router::new()
             .route("/", get(Redirect::to("/docs")))
             .nest("/v1", public_routes.merge(protected_routes))
+            .nest("/v1/hackathon", hackathon_router(db.clone(), hackathon_config))
             .merge(SwaggerUi::new("/docs").url("/openapi.json", docs_router()))
             .layer(cors_middleware())
             .layer(from_fn(security_headers_middleware))