Load chat and friend Alpine stores from IndexedDB with JSON fallback

[xylin-dev]

Motivation

• Persist and reuse conversation and friend data across page loads by reading from IndexedDB to avoid rebuilding state from server every time.
• Provide a graceful fallback to existing inline JSON script state when IndexedDB is empty or a partial load is used.

Description

• Added IndexedDB read helpers getFriendsFromDB, getChatsFromDB, and generic getObjectsFromDB in static/db.js to fetch stored records.
• Introduced getJsonScriptData helper and updated loadFull to read JSON script tags (states/friends) and await persisting them with putFriendsToDB/putChatsToDB in static/stores.js.
• Hydrate the chat store from IndexedDB via loadFromDB and add loadPartial which merges DB data with partial_states and persists partial states to IndexedDB.
• Reworked the friend store to maintain both an iteration-friendly array friends and a lookup map friendMap, added loadFromDB and init to auto-hydrate on setup, and ensured both stores call init() when created.
• Modified files: static/db.js and static/stores.js (see getFriendsFromDB, getChatsFromDB, getObjectsFromDB, getJsonScriptData, loadFromDB, loadPartial, store init changes).

Testing

• No automated tests were executed for this change.

---

Codex Task