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-hackathon/src/invitations/infrastructure/http/routes.rs

@@ -0,0 +1,23 @@
+use axum::{middleware::from_fn, routing::{get, post}, Extension, Router};
+use sqlx::PgPool;
+use std::sync::Arc;
+use crate::invitations::application::invitation_service::InvitationServiceImpl;
+use crate::invitations::domain::service::InvitationService;
+use crate::invitations::infrastructure::persistence::PostgresInvitationRepository;
+use crate::common::hackathon_jwt::HackathonJwtService;
+use crate::middleware::hackathon_auth::hackathon_auth_middleware;
+use super::handlers::*;
+
+pub fn build_invitation_routes(pool: Arc<PgPool>, jwt: Arc<HackathonJwtService>) -> Router {
+    let service: Arc<dyn InvitationService> = Arc::new(InvitationServiceImpl::new(
+        Arc::new(PostgresInvitationRepository::new(pool.clone())),
+    ));
+    Router::new()
+        .route("/invitations/my", get(get_my_invitations_handler))
+        .route("/invitations/:invitation_id/respond", post(respond_to_invitation_handler))
+        .route("/invitations/teams/:team_id/invite", post(invite_team_member_handler))
+        .layer(Extension(service))
+        .layer(Extension(jwt.clone()))
+        .layer(Extension(pool))
+        .layer(from_fn(hackathon_auth_middleware))
+}