## Summary
- Add the `config_kv` schema and Drizzle migration `0020`.
- Keep the ConfigKV schema, cache store, and invalidation contract in
the Resource API.
- Read ConfigKV through a five-minute Redis cache with PostgreSQL
fallback.
- Reload Router and TTS voice state through `configkv:invalidate`.
- Keep Auth rate limits fixed at 20 requests per 60 seconds.
## Stack
- Depends on #2294 for the Redis test implementation.
- This PR adds ConfigKV-specific cache-aside and Pub/Sub tests on top of
that implementation.
## Deployment
Run migration `0020` before this runtime reaches production traffic.
Then freeze ConfigKV writes. Audit and backfill the data with
[proj-airi/backend#2](https://github.com/proj-airi/backend/pull/2).
Merge
[proj-airi/backend#4](https://github.com/proj-airi/backend/pull/4)
first, so
the fixed Auth rate-limit keys are skipped.
Keep writes frozen until the hashes match and two API instances pass the
Pub/Sub reload check. This PR does not run production DDL or data
migration.
## Verification
- `pnpm exec vitest run <ConfigKV cache store, sync subscriber, and Auth
rate-limit tests>` (12 tests passed)
- `pnpm -F @proj-airi/api-server typecheck`
- `git diff --check`
See #2294 for its frozen-install, ESLint, and 73-test verification.
## Visual changes
None. This PR changes backend persistence and rate-limit wiring only.
<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit
- **New Features**
- Added centralized configuration storage with validation, caching,
refresh, and automatic synchronization across services.
- Configuration updates now refresh related language-model and
text-to-speech settings automatically.
- **Bug Fixes**
- Improved recovery after service reconnects by clearing stale
configuration and reloading current values.
- Invalid or unavailable configuration data now produces clearer
service-unavailable responses.
- **Changes**
- Authentication rate limiting now uses a consistent limit of 20
requests per minute per client.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->
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Signed-off-by: RainbowBird <git@luoling.moe>
Signed-off-by: RainbowBird <rbxin2003@outlook.com>
