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/report_generation/models.py

@@ -1,7 +1,9 @@
 """SQLAlchemy models for report generation
 
 Tables:
-- generated_reports: Stores report metadata and generation status
+- tr_generated_reports: Stores report metadata and generation status
+
+Note: All tables use 'tr_' prefix to avoid conflicts in shared database.
 """
 from sqlalchemy import Column, String, Text, DateTime, Integer, ForeignKey, Index, JSON
 from sqlalchemy.orm import relationship
@@ -24,14 +26,14 @@ class ReportStatus(str, enum.Enum):
 class GeneratedReport(Base):
     """Generated report model for incident reports"""
 
-    __tablename__ = "generated_reports"
+    __tablename__ = "tr_generated_reports"
 
     report_id = Column(
         String(36), primary_key=True, default=lambda: str(uuid.uuid4()),
         comment="Unique report identifier (UUID)"
     )
     room_id = Column(
-        String(36), ForeignKey("incident_rooms.room_id", ondelete="CASCADE"),
+        String(36), ForeignKey("tr_incident_rooms.room_id", ondelete="CASCADE"),
         nullable=False, comment="Reference to incident room"
     )
 
@@ -92,8 +94,8 @@ class GeneratedReport(Base):
 
     # Indexes
     __table_args__ = (
-        Index("ix_generated_reports_room_date", "room_id", "generated_at"),
-        Index("ix_generated_reports_status", "status"),
+        Index("ix_tr_generated_reports_room_date", "room_id", "generated_at"),
+        Index("ix_tr_generated_reports_status", "status"),
     )
 
     def __repr__(self):