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/teams/domain/repository.rs

@@ -0,0 +1,28 @@
+use async_trait::async_trait;
+use uuid::Uuid;
+use imphnen_utils::errors::AppError;
+use super::entity::*;
+
+#[async_trait]
+pub trait TeamRepository: Send + Sync {
+    async fn create(&self, id: Uuid, leader_id: Uuid, input: CreateTeamInput) -> Result<TeamEntity, AppError>;
+    async fn find_by_id(&self, id: Uuid) -> Result<Option<TeamEntity>, AppError>;
+    async fn browse(&self, input: BrowseTeamsInput) -> Result<(Vec<TeamEntity>, i64), AppError>;
+    async fn find_by_user(&self, user_id: Uuid) -> Result<Vec<TeamEntity>, AppError>;
+    async fn update(&self, id: Uuid, input: UpdateTeamInput) -> Result<TeamEntity, AppError>;
+    async fn delete(&self, id: Uuid) -> Result<bool, AppError>;
+    async fn get_members(&self, team_id: Uuid) -> Result<Vec<TeamMemberEntity>, AppError>;
+    async fn get_leader(&self, leader_id: Uuid) -> Result<Option<TeamUserInfo>, AppError>;
+    async fn add_member(&self, team_id: Uuid, user_id: Uuid, role: &str) -> Result<(), AppError>;
+    async fn remove_member(&self, team_id: Uuid, user_id: Uuid) -> Result<(), AppError>;
+    async fn get_member_count(&self, team_id: Uuid) -> Result<i64, AppError>;
+    async fn is_member(&self, team_id: Uuid, user_id: Uuid) -> Result<bool, AppError>;
+    async fn is_leader(&self, team_id: Uuid, user_id: Uuid) -> Result<bool, AppError>;
+    async fn user_active_team_name(&self, user_id: Uuid) -> Result<Option<String>, AppError>;
+    async fn team_has_submission(&self, team_id: Uuid) -> Result<bool, AppError>;
+    async fn reject_pending_invitations_for_user(&self, user_id: Uuid) -> Result<(), AppError>;
+    async fn reject_pending_join_requests_for_user(&self, user_id: Uuid) -> Result<(), AppError>;
+    async fn get_leaders_batch(&self, leader_ids: Vec<Uuid>) -> Result<Vec<TeamUserInfo>, AppError>;
+    async fn get_member_counts_batch(&self, team_ids: Vec<Uuid>) -> Result<Vec<(Uuid, i64)>, AppError>;
+    async fn get_submitted_team_ids(&self, team_ids: Vec<Uuid>) -> Result<Vec<Uuid>, AppError>;
+}