Add shared ai-service container as AI provider intermediary

All feature containers now POST messages to ai-service (port 8010) instead
of calling AI providers directly. ai-service routes to LM Studio, Ollama,
or Anthropic based on /config/ai_service_config.json. doc-service AI
providers removed; replaced by httpx ai_client.py. Backend settings
restructured to /api/settings/ai. Frontend gets dedicated AIAdminSettingsPage
and AI Service card in AppsPage.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

features/doc-service/tests/conftest.py

@@ -75,12 +75,13 @@ MOCK_AI_RESULT = {
 
 
 @pytest.fixture
-def mock_ai():
-    """Patch the AI classify_document call to return MOCK_AI_RESULT."""
-    provider_mock = AsyncMock()
-    provider_mock.classify_document = AsyncMock(return_value=MOCK_AI_RESULT)
-    with patch("app.routers.documents.get_provider", return_value=provider_mock):
-        yield provider_mock
+def mock_ai_service():
+    """Patch classify_document to return MOCK_AI_RESULT without hitting ai-service."""
+    with patch(
+        "app.services.ai_client.classify_document",
+        new=AsyncMock(return_value=MOCK_AI_RESULT),
+    ) as mock:
+        yield mock
 
 
 # ── HTTP client ────────────────────────────────────────────────────────────────

features/doc-service/tests/test_documents.py

@@ -189,7 +189,7 @@ async def test_cannot_assign_other_users_category(client, other_client, minimal_
 
 # ── AI processing integration (with mock AI) ──────────────────────────────────
 
-async def test_processing_sets_extracted_data(client, invoice_pdf, mock_ai):
+async def test_processing_sets_extracted_data(client, invoice_pdf, mock_ai_service):
     """Upload + wait for background processing; verify extracted_data is populated."""
     r = await client.post("/documents/upload", files=_pdf_upload("invoice.pdf", invoice_pdf))
     assert r.status_code == 202
@@ -217,9 +217,35 @@ async def test_processing_sets_extracted_data(client, invoice_pdf, mock_ai):
     assert len(extracted["suggested_categories"]) > 0
 
 
+# ── Graceful degradation when ai-service is unavailable ──────────────────────
+
+async def test_processing_fails_gracefully_when_ai_service_502(client, invoice_pdf):
+    """When ai-service returns an error, document status should be 'failed', not crash."""
+    from app.services.ai_client import AIServiceError
+
+    with patch(
+        "app.services.ai_client.classify_document",
+        side_effect=AIServiceError("ai-service returned 502"),
+    ):
+        r = await client.post("/documents/upload", files=_pdf_upload("fail.pdf", invoice_pdf))
+    assert r.status_code == 202
+    doc_id = r.json()["id"]
+
+    import asyncio
+    for _ in range(20):
+        status_r = await client.get(f"/documents/{doc_id}/status")
+        if status_r.json()["status"] in ("done", "failed"):
+            break
+        await asyncio.sleep(0.1)
+
+    doc = (await client.get(f"/documents/{doc_id}")).json()
+    assert doc["status"] == "failed"
+    assert "ai-service" in (doc.get("error_message") or "").lower()
+
+
 # ── Live tests (require real PDFs in tests/pdfs/) ─────────────────────────────
 
-async def test_live_upload_real_pdf(client, real_pdfs, mock_ai):
+async def test_live_upload_real_pdf(client, real_pdfs, mock_ai_service):
     """Upload each real PDF from tests/pdfs/ and verify it reaches 'done'."""
     import asyncio
     for pdf_path in real_pdfs: