feat(core): add anthropic provider (#11911)

Close [AI-40](https://linear.app/affine-design/issue/AI-40).

### What changed?
- Add anthropic provider.

<!-- This is an auto-generated comment: release notes by coderabbit.ai -->
## Summary by CodeRabbit

- **New Features**
  - Added support for Anthropic as a new provider option in Copilot, enabling integration with Anthropic's text generation models.
  - Users can now configure Anthropic provider settings, including API key management, through the admin interface.

- **Chores**
  - Updated dependencies to include the Anthropic SDK for backend operations.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

packages/backend/server/src/plugins/copilot/config.ts

@@ -3,6 +3,7 @@ import {
   StorageJSONSchema,
   StorageProviderConfig,
 } from '../../base';
+import { AnthropicConfig } from './providers/anthropic';
 import type { FalConfig } from './providers/fal';
 import { GeminiConfig } from './providers/gemini';
 import { OpenAIConfig } from './providers/openai';
@@ -21,6 +22,7 @@ declare global {
         fal: ConfigItem<FalConfig>;
         gemini: ConfigItem<GeminiConfig>;
         perplexity: ConfigItem<PerplexityConfig>;
+        anthropic: ConfigItem<AnthropicConfig>;
       };
     };
   }
@@ -56,6 +58,12 @@ defineModuleConfig('copilot', {
       apiKey: '',
     },
   },
+  'providers.anthropic': {
+    desc: 'The config for the anthropic provider.',
+    default: {
+      apiKey: '',
+    },
+  },
   unsplash: {
     desc: 'The config for the unsplash key.',
     default: {