chore(tests): normalize recording IDs and timestamps to reduce git diff noise (#3676)

IDs are now deterministic hashes based on request content, and
timestamps are normalized to constants, eliminating spurious changes
when re-recording tests.

## Changes
- Updated `inference_recorder.py` to normalize IDs and timestamps during
recording
- Added `scripts/normalize_recordings.py` utility to re-normalize
existing recordings
- Created documentation in `tests/integration/recordings/README.md`
- Normalized 350 existing recording files

tests/integration/recordings/responses/53d2488c9ea9.json

@@ -20,7 +20,7 @@
         "__type__": "ollama._types.GenerateResponse",
         "__data__": {
           "model": "llama3.2:3b-instruct-fp16",
-          "created_at": "2025-10-01T20:38:48.732564955Z",
+          "created_at": "1970-01-01T00:00:00.000000Z",
           "done": true,
           "done_reason": "load",
           "total_duration": null,