fix: recover after key-package exhaustion [WPB-27396]

[e-maad]

WPB-27396 [Web] Recover MLS conversations after key-package exhaustion

Summary

Fixes WPB-27396 by recovering MLS conversations that may have missed Welcome messages while the client had no available key packages.

Changes

• Detect when the backend MLS key-package count reaches zero.
• Refill key packages and persist an account-scoped recovery marker in Core DB.
• Refresh the complete conversation list to discover conversations created during key-package exhaustion.
• Audit active MLS and mixed-protocol conversations in batches of 10.
• Rejoin locally missing MLS groups using the existing external-commit flow.
• Track pending conversation IDs so interrupted recovery resumes with the remaining conversations.
• Retry recovery after startup, reconnect, window focus, or returning to the foreground.
• Pause recovery while the application is inactive.
• Continue processing after individual conversation failures and retain recovery state for another attempt.
• Clear recovery state only after the entire audit completes successfully.

Tests

Added coverage for:

• Zero key-package detection and successful refill.
• Normal low-count refills that should not trigger recovery.
• Upload and persistence failures.
• Recovery across application restarts.
• Pending-conversation progress tracking.
• MLS and mixed-protocol conversation recovery.
• Skipping Proteus, past-member, and already-established conversations.
• Pausing in the background and continuing after individual failures.