refactor: centralize auth system across all modules

All modules now use the main IAM JWT (ACCESS_TOKEN_SECRET) for authentication,
removing three separate auth systems (hackathon Supabase, hackathon JWT, QR JWT).

Changes:
- hackathon: replace HackathonJwtService with decode_access_token() from imphnen-libs
  - remove entire src/auth/ (Supabase signup/login/GitHub/forgot-reset)
  - remove common/hackathon_jwt.rs, common/supabase_client.rs
  - remove Supabase from HackathonConfig (JWT, GitHub OAuth, Supabase anon/service keys)
  - replace Supabase Storage with MinioService from imphnen-libs
  - all route jwt params removed; hackathon_router takes MinioService instead
- qr: replace QrJwtService with decode_access_token() from imphnen-libs
  - remove entire src/auth/ (register/login/Google OAuth/refresh)
  - remove common/qr_jwt.rs, src/config.rs
  - qr_auth_middleware now lazy-upserts users into QR DB on first access
  - qr_router(pool) — no config needed
- gateway: create MinioService once and pass to hackathon_router; qr_router simplified

Users now register/login via /v1/auth/* and use the same JWT for all endpoints.

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

imphnen-hackathon/Cargo.toml

@@ -7,7 +7,6 @@ edition = "2024"
 imphnen-utils.workspace = true
 imphnen-libs.workspace = true
 axum.workspace = true
-axum-extra.workspace = true
 sea-orm.workspace = true
 sqlx.workspace = true
 async-trait.workspace = true
@@ -20,6 +19,5 @@ tokio.workspace = true
 reqwest.workspace = true
 lettre.workspace = true
 base64.workspace = true
-jsonwebtoken.workspace = true
 tracing.workspace = true
 thiserror.workspace = true