feat(mcp): add collapsible additional info section in form modal

Improves UX by collapsing optional metadata fields (description, tags, homepage, docs) behind an expandable "Additional Info" section.

Changes:
- Add collapsible section with ChevronUp/ChevronDown icons
- Smart default state: collapsed for new entries, expanded for existing entries with metadata
- Add i18n keys: mcp.form.additionalInfo (zh: "附加信息", en: "Additional Info")
- Keep core fields (ID, name, config) always visible for better focus

Benefits:
- Cleaner, less cluttered form interface
- Users can focus on essential configuration first
- Optional metadata easily accessible when needed

src/i18n/locales/en.json

@@ -291,6 +291,7 @@
       "homepagePlaceholder": "https://example.com",
       "docs": "Docs",
       "docsPlaceholder": "https://example.com/docs",
+      "additionalInfo": "Additional Info",
       "jsonConfig": "JSON Configuration",
       "jsonPlaceholder": "{\n  \"type\": \"stdio\",\n  \"command\": \"uvx\",\n  \"args\": [\"mcp-server-fetch\"]\n}",
       "tomlConfig": "TOML Configuration",

src/i18n/locales/zh.json

@@ -291,6 +291,7 @@
       "homepagePlaceholder": "https://example.com",
       "docs": "文档链接",
       "docsPlaceholder": "https://example.com/docs",
+      "additionalInfo": "附加信息",
       "jsonConfig": "JSON 配置",
       "jsonPlaceholder": "{\n  \"type\": \"stdio\",\n  \"command\": \"uvx\",\n  \"args\": [\"mcp-server-fetch\"]\n}",
       "tomlConfig": "TOML 配置",