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>

Cargo.lock

@@ -1604,6 +1604,7 @@ dependencies = [
  "imphnen-dimentorin",
  "imphnen-entities",
  "imphnen-gacha",
+ "imphnen-hackathon",
  "imphnen-iam",
  "imphnen-libs",
  "imphnen-middleware",
@@ -1619,6 +1620,31 @@ dependencies = [
  "utoipa-swagger-ui",
 ]
 
+[[package]]
+name = "imphnen-hackathon"
+version = "0.2.0"
+dependencies = [
+ "async-trait",
+ "axum",
+ "axum-extra",
+ "base64",
+ "chrono",
+ "imphnen-libs",
+ "imphnen-utils",
+ "jsonwebtoken",
+ "lettre",
+ "reqwest",
+ "sea-orm",
+ "serde",
+ "serde_json",
+ "sqlx",
+ "thiserror 2.0.17",
+ "tokio",
+ "tracing",
+ "utoipa",
+ "uuid",
+]
+
 [[package]]
 name = "imphnen-iam"
 version = "0.2.0"
@@ -4215,6 +4241,7 @@ dependencies = [
  "quote",
  "regex",
  "syn 2.0.111",
+ "uuid",
 ]
 
 [[package]]