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/realtime/models.py

@@ -1,9 +1,11 @@
 """SQLAlchemy models for realtime messaging
 
 Tables:
-- messages: Stores all messages sent in incident rooms
-- message_reactions: User reactions to messages (emoji)
-- message_edit_history: Audit trail for message edits
+- tr_messages: Stores all messages sent in incident rooms
+- tr_message_reactions: User reactions to messages (emoji)
+- tr_message_edit_history: Audit trail for message edits
+
+Note: All tables use 'tr_' prefix to avoid conflicts in shared database.
 """
 from sqlalchemy import Column, Integer, String, Text, DateTime, Enum, ForeignKey, UniqueConstraint, Index, BigInteger, JSON
 from sqlalchemy.orm import relationship
@@ -25,10 +27,10 @@ class MessageType(str, enum.Enum):
 class Message(Base):
     """Message model for incident room communications"""
 
-    __tablename__ = "messages"
+    __tablename__ = "tr_messages"
 
     message_id = Column(String(36), primary_key=True, default=lambda: str(uuid.uuid4()))
-    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)
     sender_id = Column(String(255), nullable=False)  # User email/ID
     content = Column(Text, nullable=False)
     message_type = Column(Enum(MessageType), default=MessageType.TEXT, nullable=False)
@@ -42,7 +44,6 @@ class Message(Base):
     deleted_at = Column(DateTime)  # Soft delete timestamp
 
     # Sequence number for FIFO ordering within a room
-    # Note: Autoincrement doesn't work for non-PK in SQLite, will be set in service layer
     sequence_number = Column(BigInteger, nullable=False)
 
     # Relationships
@@ -51,22 +52,19 @@ class Message(Base):
 
     # Indexes for common queries
     __table_args__ = (
-        Index("ix_messages_room_created", "room_id", "created_at"),
-        Index("ix_messages_room_sequence", "room_id", "sequence_number"),
-        Index("ix_messages_sender", "sender_id"),
-        # PostgreSQL full-text search index on content (commented for SQLite compatibility)
-        # Note: Uncomment when using PostgreSQL with pg_trgm extension enabled
-        # Index("ix_messages_content_search", "content", postgresql_using='gin', postgresql_ops={'content': 'gin_trgm_ops'}),
+        Index("ix_tr_messages_room_created", "room_id", "created_at"),
+        Index("ix_tr_messages_room_sequence", "room_id", "sequence_number"),
+        Index("ix_tr_messages_sender", "sender_id"),
     )
 
 
 class MessageReaction(Base):
     """Message reaction model for emoji reactions"""
 
-    __tablename__ = "message_reactions"
+    __tablename__ = "tr_message_reactions"
 
     reaction_id = Column(Integer, primary_key=True, autoincrement=True)
-    message_id = Column(String(36), ForeignKey("messages.message_id", ondelete="CASCADE"), nullable=False)
+    message_id = Column(String(36), ForeignKey("tr_messages.message_id", ondelete="CASCADE"), nullable=False)
     user_id = Column(String(255), nullable=False)  # User email/ID who reacted
     emoji = Column(String(10), nullable=False)  # Emoji character or code
 
@@ -79,18 +77,18 @@ class MessageReaction(Base):
     # Constraints and indexes
     __table_args__ = (
         # Ensure unique reaction per user per message
-        UniqueConstraint("message_id", "user_id", "emoji", name="uq_message_reaction"),
-        Index("ix_message_reactions_message", "message_id"),
+        UniqueConstraint("message_id", "user_id", "emoji", name="uq_tr_message_reaction"),
+        Index("ix_tr_message_reactions_message", "message_id"),
     )
 
 
 class MessageEditHistory(Base):
     """Message edit history model for audit trail"""
 
-    __tablename__ = "message_edit_history"
+    __tablename__ = "tr_message_edit_history"
 
     edit_id = Column(Integer, primary_key=True, autoincrement=True)
-    message_id = Column(String(36), ForeignKey("messages.message_id", ondelete="CASCADE"), nullable=False)
+    message_id = Column(String(36), ForeignKey("tr_messages.message_id", ondelete="CASCADE"), nullable=False)
     original_content = Column(Text, nullable=False)  # Content before edit
     edited_by = Column(String(255), nullable=False)  # User who made the edit
 
@@ -102,5 +100,5 @@ class MessageEditHistory(Base):
 
     # Indexes
     __table_args__ = (
-        Index("ix_message_edit_history_message", "message_id", "edited_at"),
+        Index("ix_tr_message_edit_history_message", "message_id", "edited_at"),
     )