feat: Migrate to MySQL and add unified environment configuration

## Database Migration (SQLite → MySQL)
- Add Alembic migration framework
- Add 'tr_' prefix to all tables to avoid conflicts in shared database
- Remove SQLite support, use MySQL exclusively
- Add pymysql driver dependency
- Change ad_token column to Text type for long JWT tokens

## Unified Environment Configuration
- Centralize all hardcoded settings to environment variables
- Backend: Extend Settings class in app/core/config.py
- Frontend: Use Vite environment variables (import.meta.env)
- Docker: Move credentials to environment variables
- Update .env.example files with comprehensive documentation

## Test Organization
- Move root-level test files to tests/ directory:
  - test_chat_room.py → tests/test_chat_room.py
  - test_websocket.py → tests/test_websocket.py
  - test_realtime_implementation.py → tests/test_realtime_implementation.py
- Fix path references in test_realtime_implementation.py

Breaking Changes:
- CORS now requires explicit origins (no more wildcard)
- All database tables renamed with 'tr_' prefix
- SQLite no longer supported

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

docker-compose.minio.yml

@@ -1,9 +1,10 @@
 # MinIO Object Storage for Task Reporter
 # Usage: docker-compose -f docker-compose.minio.yml up -d
+#        docker-compose -f docker-compose.minio.yml --env-file .env.docker up -d
 #
 # This configuration starts MinIO for local development.
-# Access MinIO Console at: http://localhost:9001
-# S3 API endpoint at: http://localhost:9000
+# Access MinIO Console at: http://localhost:${MINIO_CONSOLE_PORT:-9001}
+# S3 API endpoint at: http://localhost:${MINIO_API_PORT:-9000}
 
 version: '3.8'
 
@@ -12,11 +13,11 @@ services:
     image: minio/minio:latest
     container_name: task-reporter-minio
     ports:
-      - "9000:9000"   # S3 API
-      - "9001:9001"   # MinIO Console
+      - "${MINIO_API_PORT:-9000}:9000"      # S3 API
+      - "${MINIO_CONSOLE_PORT:-9001}:9001"  # MinIO Console
     environment:
-      MINIO_ROOT_USER: minioadmin
-      MINIO_ROOT_PASSWORD: minioadmin
+      MINIO_ROOT_USER: ${MINIO_ROOT_USER:-minioadmin}
+      MINIO_ROOT_PASSWORD: ${MINIO_ROOT_PASSWORD:-minioadmin}
     command: server /data --console-address ":9001"
     volumes:
       - minio_data:/data
@@ -35,28 +36,40 @@ volumes:
 # Quick Start Guide
 # ============================================================================
 #
-# 1. Start MinIO:
+# 1. Start MinIO (with default settings):
 #    docker-compose -f docker-compose.minio.yml up -d
 #
-# 2. Access MinIO Console:
-#    Open http://localhost:9001 in your browser
-#    Login: minioadmin / minioadmin
+# 2. Start MinIO (with custom settings from .env.docker):
+#    docker-compose -f docker-compose.minio.yml --env-file .env.docker up -d
 #
-# 3. The application will automatically create the bucket on startup
+# 3. Access MinIO Console:
+#    Open http://localhost:9001 in your browser
+#    Login with MINIO_ROOT_USER / MINIO_ROOT_PASSWORD
+#
+# 4. The application will automatically create the bucket on startup
 #    (configured as 'task-reporter-files' in .env)
 #
-# 4. Stop MinIO:
+# 5. Stop MinIO:
 #    docker-compose -f docker-compose.minio.yml down
 #
-# 5. Remove all data:
+# 6. Remove all data:
 #    docker-compose -f docker-compose.minio.yml down -v
 #
 # ============================================================================
+# Environment Variables
+# ============================================================================
+#
+# MINIO_ROOT_USER     - MinIO admin username (default: minioadmin)
+# MINIO_ROOT_PASSWORD - MinIO admin password (default: minioadmin)
+# MINIO_API_PORT      - S3 API port (default: 9000)
+# MINIO_CONSOLE_PORT  - Web console port (default: 9001)
+#
+# ============================================================================
 # Production Notes
 # ============================================================================
 #
 # For production deployment:
-# - Change MINIO_ROOT_USER and MINIO_ROOT_PASSWORD to secure values
+# - Set secure MINIO_ROOT_USER and MINIO_ROOT_PASSWORD in .env.docker
 # - Use external volume or persistent storage
 # - Configure TLS/HTTPS
 # - Set up proper backup policies