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/chat/infrastructure/http/handlers.rs

@@ -0,0 +1,36 @@
+use axum::{Extension, Json, extract::Path, response::IntoResponse};
+use std::sync::Arc;
+use uuid::Uuid;
+use imphnen_utils::{errors::AppError, response_format::{ApiSuccess, ApiMessage}};
+use crate::middleware::hackathon_auth::HackathonAuthUser;
+use crate::chat::domain::service::ChatService;
+use super::dto::*;
+
+pub async fn get_team_messages_handler(
+    Extension(service): Extension<Arc<dyn ChatService>>,
+    Extension(auth): Extension<HackathonAuthUser>,
+    Path(team_id): Path<Uuid>,
+) -> Result<axum::response::Response, AppError> {
+    let messages = service.get_team_messages(team_id, auth.user_id).await?;
+    let response: Vec<MessageResponse> = messages.into_iter().map(MessageResponse::from).collect();
+    Ok(ApiSuccess(response).into_response())
+}
+
+pub async fn send_message_handler(
+    Extension(service): Extension<Arc<dyn ChatService>>,
+    Extension(auth): Extension<HackathonAuthUser>,
+    Path(team_id): Path<Uuid>,
+    Json(body): Json<SendMessageRequest>,
+) -> Result<axum::response::Response, AppError> {
+    let message = service.send_message(team_id, auth.user_id, body.into()).await?;
+    Ok(ApiSuccess(MessageResponse::from(message)).into_response())
+}
+
+pub async fn delete_message_handler(
+    Extension(service): Extension<Arc<dyn ChatService>>,
+    Extension(auth): Extension<HackathonAuthUser>,
+    Path(message_id): Path<Uuid>,
+) -> Result<axum::response::Response, AppError> {
+    service.delete_message(message_id, auth.user_id).await?;
+    Ok(ApiMessage::ok("Message deleted").into_response())
+}