feat(07.4-02): update api/auth.py call sites, promote FGP tests, version bump 0.1.3

- api/auth.py login + refresh call sites pass User-Agent and Accept-Language
  headers to create_access_token (D-05 — fgp binding at token issuance)
- test_auth_fgp.py: promote all 4 xfail stubs to real assertions (FGP-01..04)
- conftest.py: add _TEST_USER_AGENT constant; configure async_client to send
  consistent User-Agent; update auth_user/second_auth_user/admin_user fixtures
  to bind fgp to _TEST_USER_AGENT so tokens validate correctly in tests
- test_auth_deps.py: import _TEST_USER_AGENT; update auth_client fixture and
  all create_access_token calls to use the constant
- test_cloud.py: update _create_user_and_token to bind fgp to _TEST_USER_AGENT
- test_documents.py: update 3 inline create_access_token calls to pass user_agent
- test_security_headers.py: import _TEST_USER_AGENT; update headers_client +
  token creation to use the constant
- Version bump: backend 0.1.2 → 0.1.3, frontend 0.1.2 → 0.1.3
- [Rule 1 - Bug] Fix httpx default User-Agent vs empty-string fgp mismatch in
  test infrastructure: 10 tests were failing due to fgp check rejecting tokens
  created with fgp="" when client sent "python-httpx/X.Y.Z"

backend/tests/test_security_headers.py

@@ -18,6 +18,8 @@ import pytest_asyncio
 from httpx import ASGITransport, AsyncClient
 from sqlalchemy.ext.asyncio import AsyncSession
 
+from tests.conftest import _TEST_USER_AGENT
+
 
 # ── FakeRedis (needed by login endpoint) ─────────────────────────────────────
 
@@ -77,7 +79,12 @@ async def headers_client(db_session: AsyncSession):
     except Exception:
         pass
 
-    async with AsyncClient(transport=ASGITransport(app=app), base_url="http://test") as c:
+    # Phase 7.4: send _TEST_USER_AGENT so fgp check matches tokens from this file
+    async with AsyncClient(
+        transport=ASGITransport(app=app),
+        base_url="http://test",
+        headers={"User-Agent": _TEST_USER_AGENT},
+    ) as c:
         yield c
 
     app.dependency_overrides.clear()
@@ -173,7 +180,8 @@ async def test_security_headers_on_authenticated_route(headers_client, db_sessio
     db_session.add(quota)
     await db_session.commit()
 
-    token = create_access_token(str(user_id), "user")
+    # Phase 7.4: bind fgp to _TEST_USER_AGENT (matches headers_client default)
+    token = create_access_token(str(user_id), "user", user_agent=_TEST_USER_AGENT)
     resp = await headers_client.get(
         "/api/auth/me",
         headers={"Authorization": f"Bearer {token}"},