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/pyproject.toml

@@ -0,0 +1,29 @@
+[build-system]
+requires = ["setuptools>=45"]
+build-backend = "setuptools.build_meta"
+
+[project]
+name = "ai-service"
+version = "0.1.0"
+requires-python = ">=3.11"
+dependencies = [
+    "fastapi>=0.111",
+    "uvicorn[standard]>=0.29",
+    "pydantic-settings>=2.2",
+    "anthropic>=0.28",
+    "openai>=1.0",
+]
+
+[project.optional-dependencies]
+dev = [
+    "pytest>=8",
+    "pytest-asyncio>=0.23",
+    "httpx>=0.27",
+    "ruff>=0.4",
+]
+
+[tool.pytest.ini_options]
+asyncio_mode = "auto"
+
+[tool.ruff]
+line-length = 100