QTZPOC-20

QTZPOC-20: Implement .sientia model bundle import workflow

Introduces a new Temporal workflow and activities to import .sientia model bundles. This enables:
- Secure decryption and validation of bundles through a seven-gate process.
- Provisioning imported models in MLflow and updating the MongoDB model listing.
- Comprehensive status tracking in the public.experiment_run table with new IMPORT_SUCCESS/IMPORT_ERROR states.
- Dedicated metrics, robust error handling, and configurable settings.
- Includes updated e2e database fixtures and extensive unit/integration tests for bundle format, reader, and overall workflow.

tests/fixtures/bundle/README.md

@@ -0,0 +1,86 @@
+# Golden `.sientia` fixtures
+
+Binary conformance vectors for `laborious/utils/bundle/`. They are **bytes the producer's own code
+emitted**, not bytes this repository knows how to write: there is no production writer here (change
+`import-model-workflow`, design D1). If the producer's layout moves, the reader's tests fail against
+these files instead of failing in production.
+
+| File | What it is |
+|---|---|
+| `golden_model_v3.sientia` | `format_version` 1 bundle, 110767 bytes, plaintext zip 110569 bytes — **two chunks**, so `MESSAGE`/`FINAL` framing is exercised by the golden fixture itself |
+| `golden_model_v3.metadata.json` | the `metadata.json` that went into that bundle, in plaintext, so a test can assert the recovered value without decrypting first |
+| `regenerate.py` | the script that produced them, importing the producer's `bundle.py`/`crypto.py` by path |
+
+## Password
+
+```
+Import1Model!Fixture
+```
+
+Recorded deliberately: the fixture protects nothing. It satisfies the producer's export-side
+strength rule (≥ 12 characters, upper, lower, digit, symbol), which is checked by
+`crypto.validate_password_strength` at generation time.
+
+## Provenance
+
+- Producer repository: `sientia-projects-templates`
+- Producer commit: `8d3c1fd117c697e8b352c34f11c732809a4a129b`
+  (`8d3c1fd QTZPOC-7: adapt to lint rules picked up from merging main`)
+- Producer modules used: `app/src/operations/model_export/bundle.py`,
+  `app/src/operations/model_export/crypto.py` — loaded by path, so every constant, the `struct`
+  layout, the zip layout, the KDF parameters and the chunk framing come from the producer and none of
+  them is re-implemented here
+- Producer pin honoured: `pynacl==1.5.0` (this repository pins the same version)
+
+One deviation from task 0.3, recorded rather than hidden: the bytes were generated with the
+producer's **code** under *this* repository's venv, not inside the producer's own venv, because that
+venv has neither `pynacl` nor `mlflow` installed. The dependency that matters for the bytes is
+`pynacl`, pinned identically on both sides, and `mlflow` is not reached — `regenerate.py` builds the
+artifact tree itself instead of calling `client.download_artifacts`.
+
+## Contents of the bundle
+
+```
+metadata.json                          (written first, no indent, by bundle.build_zip)
+artifacts/prediction_model/MLmodel
+artifacts/prediction_model/model.pkl            (90 KiB of incompressible filler)
+artifacts/prediction_model/conda.yaml
+artifacts/prediction_model/python_env.yaml
+artifacts/prediction_model/requirements.txt
+artifacts/data_model/MLmodel
+artifacts/data_model/model.pkl                  (8 KiB)
+artifacts/data_model/conda.yaml
+artifacts/data_model/python_env.yaml
+artifacts/data_model/requirements.txt
+artifacts/model_card/model_card.json
+artifacts/train_data.csv
+artifacts/test_data.csv
+artifacts/raw_data.csv
+```
+
+No directory entries are stored — the producer only adds paths for which `is_file()` is true.
+
+`parameters` carries `target_variable: "SE"`, which gate 6 requires and which becomes
+`model_config.target` in the MongoDB model document.
+
+## Digest boundary — the reason this fixture exists
+
+The header's `ciphertext_digest` is `sha256(file[164:])`: the producer computes
+`hashlib.sha256(ciphertext)` over the joined chunks and only then writes
+`header + stream_header + ciphertext`, so the 24-byte `secretstream` header is **not** covered.
+Verified against this fixture and against a freshly produced bundle. Earlier prose (this change's own
+first draft, and `aig-docs/03-sientia-bundle-format.md`) said "everything after the plaintext
+header", i.e. from offset 140 — that is wrong, and `tests/laborious/utils/bundle/test_format.py`
+asserts both directions so it cannot come back.
+
+## Regenerating
+
+```bash
+source ./venv/bin/activate
+PRODUCER_REPO=../sientia-projects-templates python tests/fixtures/bundle/regenerate.py
+```
+
+Two fields change on every run and are expected to: the 16-byte salt (`os.urandom`) and
+`metadata.metadata.export_timestamp` (`datetime.now(UTC)`). Everything else is deterministic —
+the filler bytes come from a seeded PRNG. After regenerating, update the producer commit above and
+the byte counts in the table.