fix: chat.py ChatManager stores all state in-memory — messages and escalations lost on restart

[BigBen-7]

Description

src/chat.py holds all conversation history, escalation events, and active connections entirely in instance variables:

self.message_history: Dict[str, List[ChatMessage]] = {}
self.escalations: List[EscalationEvent] = []

A pod restart, dyno cycle, or deployment wipes every conversation. Users lose their support history and any pending escalations silently disappear — a critical reliability gap for a support chat system.

Requirements & context

• Create a src/chat_store.py module with a ChatStore class that persists messages and escalations to Postgres using the existing SQLAlchemy setup
• Add two new SQLAlchemy models (or Alembic migrations): chat_messages and chat_escalations tables mirroring the ChatMessage and EscalationEvent Pydantic models
• Update ChatManager.send_message to persist each message to the DB (async-safe — use asyncio.to_thread if using sync SQLAlchemy)
• Update ChatManager.get_message_history to fall back to the DB when the in-memory cache is empty (i.e. after a restart)
• Update ChatManager.escalate_conversation to persist the escalation event
• Active WebSocket connections remain in-memory (they cannot be persisted) — document this clearly

Suggested execution

git checkout -b feat/chat-persistent-storage

• Create src/chat_store.py with ChatStore
• Add SQLAlchemy models and Alembic migration
• Update ChatManager to call ChatStore for read/write operations
• Write tests confirming messages survive a simulated manager restart (new instance reads from DB)

Guidelines

• Do not change the WebSocket or HTTP API contracts
• PR must include: Closes #[issue_id]
• Timeframe: 96 hours

[demilade18-git]

@demilade18-git has applied to work on this issue as part of the Stellar Wave Program's 3rd wave.

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[drips-wave]

This issue has been completed by @demilade18-git as part of the Stellar Wave Program's 3rd Wave 🥳

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