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>

app/modules/chat_room/models.py

@@ -1,9 +1,11 @@
 """SQLAlchemy models for chat room management
 
 Tables:
-- incident_rooms: Stores room metadata and configuration
-- room_members: User-room associations with roles
-- room_templates: Predefined templates for common incident types
+- tr_incident_rooms: Stores room metadata and configuration
+- tr_room_members: User-room associations with roles
+- tr_room_templates: Predefined templates for common incident types
+
+Note: All tables use 'tr_' prefix to avoid conflicts in shared database.
 """
 from sqlalchemy import Column, Integer, String, Text, DateTime, Enum, ForeignKey, UniqueConstraint, Index
 from sqlalchemy.orm import relationship
@@ -46,7 +48,7 @@ class MemberRole(str, enum.Enum):
 class IncidentRoom(Base):
     """Incident room model for production incidents"""
 
-    __tablename__ = "incident_rooms"
+    __tablename__ = "tr_incident_rooms"
 
     room_id = Column(String(36), primary_key=True, default=lambda: str(uuid.uuid4()))
     title = Column(String(255), nullable=False)
@@ -80,18 +82,18 @@ class IncidentRoom(Base):
 
     # Indexes for common queries
     __table_args__ = (
-        Index("ix_incident_rooms_status_created", "status", "created_at"),
-        Index("ix_incident_rooms_created_by", "created_by"),
+        Index("ix_tr_incident_rooms_status_created", "status", "created_at"),
+        Index("ix_tr_incident_rooms_created_by", "created_by"),
     )
 
 
 class RoomMember(Base):
     """Room membership model"""
 
-    __tablename__ = "room_members"
+    __tablename__ = "tr_room_members"
 
     id = Column(Integer, primary_key=True, autoincrement=True)
-    room_id = Column(String(36), ForeignKey("incident_rooms.room_id", ondelete="CASCADE"), nullable=False)
+    room_id = Column(String(36), ForeignKey("tr_incident_rooms.room_id", ondelete="CASCADE"), nullable=False)
     user_id = Column(String(255), nullable=False)  # User email/ID
     role = Column(Enum(MemberRole), nullable=False)
 
@@ -106,16 +108,16 @@ class RoomMember(Base):
     # Constraints and indexes
     __table_args__ = (
         # Ensure unique active membership (where removed_at IS NULL)
-        UniqueConstraint("room_id", "user_id", "removed_at", name="uq_room_member_active"),
-        Index("ix_room_members_room_user", "room_id", "user_id"),
-        Index("ix_room_members_user", "user_id"),
+        UniqueConstraint("room_id", "user_id", "removed_at", name="uq_tr_room_member_active"),
+        Index("ix_tr_room_members_room_user", "room_id", "user_id"),
+        Index("ix_tr_room_members_user", "user_id"),
     )
 
 
 class RoomTemplate(Base):
     """Predefined templates for common incident types"""
 
-    __tablename__ = "room_templates"
+    __tablename__ = "tr_room_templates"
 
     template_id = Column(Integer, primary_key=True, autoincrement=True)
     name = Column(String(100), unique=True, nullable=False)