feat(07.3-02): ES256 JWT algorithm upgrade + startup rotation hook

- config.py: add refresh_token_expire_hours=16, jwt_private_key, jwt_public_key fields (D-01, D-09)
- services/auth.py: swap all 4 JWT sites to ES256 via base64-decoded PEM keys; remove HS256 (D-02, D-03)
- main.py: add _rotate_tokens_on_algorithm_change lifespan hook — bulk-revokes refresh tokens on algorithm change; idempotent on repeat boots (D-04, D-05)
- test_auth_es256.py: promote ES256-01..05 + CFG-01 stubs to 6 passing tests; RM-01..03 remain xfail
- docker-compose.yml: inject JWT_PRIVATE_KEY + JWT_PUBLIC_KEY into backend + celery-worker (D-07)
- README.md: add JWT key env vars + key generation Python one-liner snippet
- .env.example: add JWT_PRIVATE_KEY= and JWT_PUBLIC_KEY= lines
- Version bump to 0.1.2

backend/main.py

@@ -12,7 +12,7 @@ from minio import Minio
 from slowapi import _rate_limit_exceeded_handler
 from slowapi.errors import RateLimitExceeded
 from slowapi.middleware import SlowAPIMiddleware
-from sqlalchemy import text
+from sqlalchemy import select, text
 from starlette.middleware.base import BaseHTTPMiddleware
 from starlette.responses import Response as StarletteResponse
 from starlette.types import ASGIApp, Receive, Scope, Send
@@ -130,6 +130,50 @@ class CorrelationIDMiddleware:
         )
 
 
+# ── ES256 startup rotation helper ────────────────────────────────────────────
+
+async def _rotate_tokens_on_algorithm_change(session) -> None:
+    """Idempotent ES256 migration (Phase 7.3 D-04/D-05).
+
+    On every boot, compares the jwt_algorithm marker row in system_settings against
+    'ES256'. If absent or different, bulk-revokes all active refresh tokens via raw
+    SQL UPDATE and upserts the marker (with is_active=False so the AI provider loader
+    never returns this row). No-op on second boot.
+    """
+    import logging as _logging
+    from db.models import SystemSettings  # noqa: PLC0415
+
+    stmt = select(SystemSettings).where(SystemSettings.provider_id == "jwt_algorithm")
+    result = await session.execute(stmt)
+    row = result.scalar_one_or_none()
+
+    if row is not None and row.model_name == "ES256":
+        return  # idempotent — algorithm already matches
+
+    # Bulk-revoke all active refresh tokens (single raw SQL — no Python iteration)
+    _logging.getLogger(__name__).info(
+        "ES256 startup rotation: bulk-revoked all active refresh tokens"
+    )
+    await session.execute(
+        text("UPDATE refresh_tokens SET revoked = true WHERE revoked = false")
+    )
+
+    if row is None:
+        session.add(SystemSettings(
+            id=uuid.uuid4(),
+            provider_id="jwt_algorithm",
+            model_name="ES256",
+            context_chars=0,
+            is_active=False,
+            api_key_enc=None,
+            base_url=None,
+        ))
+    else:
+        row.model_name = "ES256"
+
+    await session.commit()
+
+
 # ── Lifespan ──────────────────────────────────────────────────────────────────
 
 @asynccontextmanager
@@ -179,6 +223,18 @@ async def lifespan(app: FastAPI):
             "AI provider seed skipped (table may not exist yet): %s", _seed_exc
         )
 
+    # ES256 algorithm rotation (Phase 7.3 D-04/D-05): bulk-revoke on algorithm change.
+    # Wrapped in try/except — fresh containers may not have system_settings table yet
+    # (Pitfall 6 in RESEARCH.md).
+    try:
+        async with AsyncSessionLocal() as session:
+            await _rotate_tokens_on_algorithm_change(session)
+    except Exception as _es256_exc:
+        import logging as _logging
+        _logging.getLogger(__name__).warning(
+            "ES256 rotation check skipped (table may not exist yet): %s", _es256_exc
+        )
+
     yield
 
     # Shutdown: close pooled connections and Redis
@@ -188,7 +244,7 @@ async def lifespan(app: FastAPI):
 
 # ── Application factory ───────────────────────────────────────────────────────
 
-app = FastAPI(title="Document Scanner API", version="0.1.1", lifespan=lifespan)
+app = FastAPI(title="Document Scanner API", version="0.1.2", lifespan=lifespan)
 
 # Rate limiter state (slowapi)
 app.state.limiter = auth_limiter