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/providers/openai_compat.py

@@ -0,0 +1,52 @@
+"""OpenAI-compatible provider — handles both Ollama and LM Studio."""
+import asyncio
+
+import openai
+
+from app.providers.base import AIProvider
+from app.schemas.chat import ChatMessage
+
+
+class OpenAICompatProvider(AIProvider):
+    def __init__(self, config: dict, provider_name: str = "lmstudio") -> None:
+        self._client = openai.AsyncOpenAI(
+            base_url=config.get("base_url", "http://localhost:1234/v1"),
+            api_key=config.get("api_key") or "not-required",
+        )
+        self.model_name = config.get("model", "local-model")
+        self.provider_name = provider_name
+
+    async def chat(
+        self,
+        messages: list[ChatMessage],
+        max_tokens: int,
+        temperature: float,
+    ) -> tuple[str, int | None, int | None]:
+        raw_messages = [{"role": m.role, "content": m.content} for m in messages]
+        try:
+            response = await self._client.chat.completions.create(
+                model=self.model_name,
+                messages=raw_messages,
+                max_tokens=max_tokens,
+                temperature=temperature,
+            )
+        except openai.APIConnectionError as exc:
+            raise ProviderConnectionError(str(exc)) from exc
+        except openai.APITimeoutError as exc:
+            raise ProviderTimeoutError(str(exc)) from exc
+        except openai.APIStatusError as exc:
+            raise ProviderConnectionError(f"API error {exc.status_code}: {exc.message}") from exc
+
+        content = response.choices[0].message.content or ""
+        usage = response.usage
+        input_tokens = usage.prompt_tokens if usage else None
+        output_tokens = usage.completion_tokens if usage else None
+        return content, input_tokens, output_tokens
+
+
+class ProviderConnectionError(Exception):
+    pass
+
+
+class ProviderTimeoutError(Exception):
+    pass