feat(i18n): complete internationalization for MCP preset descriptions

- Add i18n keys for all 5 MCP preset descriptions (fetch, time, memory, sequential-thinking, context7)
- Refactor mcpPresets.ts to use i18n keys instead of hardcoded Chinese descriptions
- Add getMcpPresetWithDescription() helper function for dynamic translation
- Update McpFormModal to use translated descriptions when applying presets
- Fix inconsistent key naming: sequentialThinking -> sequential-thinking

This ensures MCP preset descriptions automatically switch language based on user's locale setting.

src/i18n/locales/en.json

@@ -362,7 +362,27 @@
       "enabled": "Enabled",
       "installed": "Installed",
       "docs": "Docs",
-      "requiresEnv": "Requires env"
+      "requiresEnv": "Requires env",
+      "fetch": {
+        "name": "mcp-server-fetch",
+        "description": "Universal HTTP request tool, supports GET/POST and other HTTP methods, suitable for quick API requests and web data scraping"
+      },
+      "time": {
+        "name": "@modelcontextprotocol/server-time",
+        "description": "Time query tool providing current time, timezone conversion, and date calculation features"
+      },
+      "memory": {
+        "name": "@modelcontextprotocol/server-memory",
+        "description": "Knowledge graph memory system supporting entities, relations, and observations to help AI remember important information from conversations"
+      },
+      "sequential-thinking": {
+        "name": "@modelcontextprotocol/server-sequential-thinking",
+        "description": "Sequential thinking tool helping AI break down complex problems into multiple steps for deeper thinking"
+      },
+      "context7": {
+        "name": "@upstash/context7-mcp",
+        "description": "Context7 documentation search tool providing latest library docs and code examples, with higher limits when configured with a key"
+      }
     }
   }
 }