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/ai-service/tests/test_health.py

@@ -0,0 +1,38 @@
+"""Tests for GET /health and GET /health/provider."""
+from unittest.mock import patch
+
+import pytest
+
+from tests.conftest import ANTHROPIC_CONFIG, LMSTUDIO_CONFIG, MISSING_KEY_ANTHROPIC_CONFIG
+
+_LOAD_CONFIG = "app.routers.health.load_ai_config"
+
+
+@pytest.mark.asyncio
+async def test_health_returns_ok(ai_client):
+    resp = await ai_client.get("/health")
+    assert resp.status_code == 200
+    assert resp.json() == {"status": "ok"}
+
+
+@pytest.mark.asyncio
+async def test_provider_status_configured(ai_client):
+    with patch(_LOAD_CONFIG, return_value=LMSTUDIO_CONFIG):
+        resp = await ai_client.get("/health/provider")
+
+    assert resp.status_code == 200
+    data = resp.json()
+    assert data["provider"] == "lmstudio"
+    assert data["model"] == "test-model"
+    assert data["configured"] is True
+
+
+@pytest.mark.asyncio
+async def test_provider_status_not_configured_when_api_key_missing(ai_client):
+    with patch(_LOAD_CONFIG, return_value=MISSING_KEY_ANTHROPIC_CONFIG):
+        resp = await ai_client.get("/health/provider")
+
+    assert resp.status_code == 200
+    data = resp.json()
+    assert data["provider"] == "anthropic"
+    assert data["configured"] is False