Persist dashboard chat history across refreshes

[iamagenius00]

Problem

The dashboard chat UI does not persist conversation history. Three concrete issues:

1. History is lost on refresh — reloading the dashboard clears the current conversation.
2. History bleeds across models — switching between models can show the wrong conversation, since history isn't isolated per model.
3. UI gets stuck mid-generation — if the page is refreshed while a response is streaming, messages remain frozen in a thinking / generating / waiting state with no way to recover.

Proposal

Persist chat messages to the browser's localStorage, keyed by model name:

• Save messages per modelName (storage key scoped to the active model).
• Restore the current model's history automatically on load.
• Isolate history per model, so switching models never mixes conversations.
• On restore, normalize any unfinished waiting / thinking / generating message back to done, so a refresh during generation doesn't leave the UI stuck.

This is a client-only change in the dashboard frontend (src/frontend/src/services/chat.tsx) — no backend or API changes.

Status

Implemented locally; a PR will follow. Happy to adjust the storage key scheme, versioning, or eviction policy based on maintainer preference.