[LSaiko]

Replaces the in-memory projects dict with a persistent store. The API, the Pydantic schemas and the Archivist's behaviour are unchanged.

Changes

• app/store.py defines the TraceabilityStore protocol (get/put) and two implementations:
  • InMemoryStore
  • SqliteStore, which uses stdlib sqlite3 and keeps one table per stored record type, with columns that mirror the Pydantic fields.
• Setup: an idempotent CREATE TABLE IF NOT EXISTS runs on startup, or standalone with python -m app.store.
• DB file: DHF_DB_PATH, default data/dhf.db, which is gitignored.
• app/main.py: each endpoint gets the store through Depends(get_store). The server opens SqliteStore at startup, so there is no global.
• Tests: plain pytest runs the fast suite against InMemoryStore. pytest -m integration covers:
  • a round trip of every record type across a store restart, compared byte-for-byte
  • the API end to end across an app restart
• CI: runs both suites and fails if combined coverage drops below 100%, so the badge stays accurate.
• Docs: the README and docs/architecture.md describe the persistence model and its limits.

Not changed

• Trace links and gaps are still recomputed by build_matrix on every read and are not stored, so the gap report can't go stale.
• The GitHub Pages demo is a static seed build with no backend, so it is unaffected.

Known limits (also in the README)

• No locking for concurrent writes. When two writes hit the same project at once, the last one wins, and two simultaneous evidence uploads can both be numbered VAL-n. Only single-writer use has been tested.
• No revision history or audit trail. A write replaces the project's current records, so this is not yet a configuration-managed record under 21 CFR 820.30(j) / IEC 62304 §8.
• No schema changes after creation. If a model gains a field, an existing DB needs a manual ALTER TABLE or a fresh file.

Verification

• CI is green on the branch (Python 3.12 and 3.13, dashboard).
• Combined coverage is 100%.
• Manual check: stopped and restarted uvicorn, and the data was still there.

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