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/anthropic_provider.py

@@ -0,0 +1,54 @@
+import asyncio
+
+import anthropic
+
+from app.providers.base import AIProvider
+from app.schemas.chat import ChatMessage
+
+
+class AnthropicProvider(AIProvider):
+    def __init__(self, config: dict) -> None:
+        self._client = anthropic.AsyncAnthropic(api_key=config.get("api_key", ""))
+        self.model_name = config.get("model", "claude-haiku-4-5-20251001")
+        self.provider_name = "anthropic"
+
+    async def chat(
+        self,
+        messages: list[ChatMessage],
+        max_tokens: int,
+        temperature: float,
+    ) -> tuple[str, int | None, int | None]:
+        # Anthropic uses a top-level `system=` param, not a role in the messages array
+        system_content = ""
+        user_messages = []
+        for msg in messages:
+            if msg.role == "system":
+                system_content += msg.content + "\n"
+            else:
+                user_messages.append({"role": msg.role, "content": msg.content})
+
+        try:
+            response = await self._client.messages.create(
+                model=self.model_name,
+                max_tokens=max_tokens,
+                temperature=temperature,
+                system=system_content.strip() or anthropic.NOT_GIVEN,
+                messages=user_messages,
+            )
+        except anthropic.APIConnectionError as exc:
+            raise ProviderConnectionError(str(exc)) from exc
+        except anthropic.APITimeoutError as exc:
+            raise ProviderTimeoutError(str(exc)) from exc
+        except anthropic.APIStatusError as exc:
+            raise ProviderConnectionError(f"Anthropic API error {exc.status_code}: {exc.message}") from exc
+
+        content = response.content[0].text
+        return content, response.usage.input_tokens, response.usage.output_tokens
+
+
+class ProviderConnectionError(Exception):
+    pass
+
+
+class ProviderTimeoutError(Exception):
+    pass