Implement RecorderPolicy and Integrate with Resilience Chain

## Motivation

Resilience operations need to automatically record their outcomes to the RequestRecorder. A new policy in the resilience chain can transparently capture this information.

- No automatic recording of resilience operation results
- Manual recording would require changes to every decorated method

## Required Features

- Create `RecorderPolicy` class extending base `Policy`
- Record operation name, success/failure status, duration, and error message
- Gracefully handle case when no recorder context is active (skip recording)
- Add RecorderPolicy to existing client resilience configurations
- Position in chain: typically after MetricPolicy, before RetryPolicy

## Impact

- New file: `src/ai/backend/common/resilience/policies/recorder.py`
- `src/ai/backend/common/resilience/policies/__init__.py`
- `src/ai/backend/manager/clients/agent/client.py`
- `src/ai/backend/manager/clients/storage_proxy/manager_facing_client.py`
- `src/ai/backend/manager/clients/appproxy/client.py`

## Testing Scenarios

- Test RecorderPolicy records success with duration
- Test RecorderPolicy records failure with error message
- Test policy works correctly without active recorder context
- Integration test with full resilience chain

JIRA Issue: BA-3729