fix(i18n): add missing Gemini MCP panel title and fix ternary logic

- Add mcp.geminiTitle to both zh.json and en.json
- Fix McpPanel title logic to handle all three apps (claude/codex/gemini)
- Previous logic would incorrectly display codexTitle for gemini

src/i18n/locales/zh.json

@@ -440,6 +440,7 @@
     "title": "MCP 管理",
     "claudeTitle": "Claude Code MCP 管理",
     "codexTitle": "Codex MCP 管理",
+    "geminiTitle": "Gemini MCP 管理",
     "userLevelPath": "用户级 MCP 配置路径",
     "serverList": "服务器列表",
     "loading": "加载中...",