fix(server): index & gc queue & llm compatibility (#15528)

fix #15523
fix #15526

#### PR Dependency Tree


* **PR #15528** 👈

This tree was auto-generated by
[Charcoal](https://github.com/danerwilliams/charcoal)

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit

- **Bug Fixes**
- Improved search generation cleanup, provider error reporting, and
reconciliation reliability.
- Retired search resources are cleaned up safely, including after
credential changes.
- Prompt size checks now ignore tool parameters and provide clearer
errors.
- Reserved documents are protected from accidental cleanup, and
malformed identifiers are rejected.

- **Configuration**
- Managed Copilot profiles require explicit, non-duplicated model
assignments.
  - Improved managed provider profile migration.

- **Performance & Reliability**
- Reduced unnecessary search-history cleanup and adjusted
consistency-check intervals.
- Failed reconciliation jobs stop after one attempt and are removed
automatically.

- **Data Updates**
  - Updated legacy AI session prompt names to current labels.
  - Improved cloud load-balancer health-check configuration.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

packages/backend/server/migrations/20260826120000_migrate_legacy_copilot_prompt_names/migration.sql

@@ -0,0 +1,20 @@
+UPDATE ai_sessions_metadata
+SET prompt_name = CASE prompt_name
+  WHEN 'Search With AFFiNE AI' THEN 'Chat With AFFiNE AI'
+  WHEN 'debug:action:dalle3' THEN 'Generate image'
+  WHEN 'debug:action:fal-sd15' THEN 'Generate image'
+  WHEN 'debug:action:gpt-image-1' THEN 'Generate image'
+  WHEN 'debug:action:fal-remove-bg' THEN 'Remove background'
+  WHEN 'debug:action:fal-upscaler' THEN 'Upscale image'
+  WHEN 'debug:action:fal-face-to-sticker' THEN 'Convert to sticker'
+  ELSE prompt_name
+END
+WHERE prompt_name IN (
+  'Search With AFFiNE AI',
+  'debug:action:dalle3',
+  'debug:action:fal-sd15',
+  'debug:action:gpt-image-1',
+  'debug:action:fal-remove-bg',
+  'debug:action:fal-upscaler',
+  'debug:action:fal-face-to-sticker'
+);