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/app/main.py

@@ -0,0 +1,25 @@
+import logging
+from contextlib import asynccontextmanager
+
+from fastapi import FastAPI
+
+from app.core.config import settings
+from app.routers import chat, health
+from app.services.config_reader import load_ai_config
+
+logger = logging.getLogger("ai-service")
+
+
+@asynccontextmanager
+async def lifespan(app: FastAPI):
+    config = await load_ai_config()
+    provider = config.get("provider", "lmstudio")
+    model = config.get(provider, {}).get("model", "unknown")
+    logger.info("[ai-service] active provider: %s  model: %s", provider, model)
+    yield
+
+
+app = FastAPI(title=settings.PROJECT_NAME, lifespan=lifespan)
+
+app.include_router(chat.router, tags=["chat"])
+app.include_router(health.router, tags=["health"])