feat: add inline citations and thread management features

Citations:
- Add citations parsing utilities for extracting source references from AI responses
- Render inline citations as hover card badges in message content
- Display citation cards with title, URL, and description on hover
- Add citation badge rendering in artifact markdown preview
- Update prompt to guide AI to output citations in correct format

Thread Management:
- Add rename functionality for chat threads with dialog UI
- Add share functionality to copy thread link to clipboard
- Share links use Vercel URL for production accessibility
- Add useRenameThread hook for thread title updates

i18n:
- Add translations for rename, share, cancel, save, and linkCopied

Co-authored-by: Cursor <cursoragent@cursor.com>

frontend/src/core/i18n/locales/en-US.ts

@@ -11,6 +11,8 @@ export const enUS: Translations = {
     home: "Home",
     settings: "Settings",
     delete: "Delete",
+    rename: "Rename",
+    share: "Share",
     openInNewWindow: "Open in new window",
     close: "Close",
     more: "More",
@@ -24,6 +26,8 @@ export const enUS: Translations = {
     loading: "Loading...",
     code: "Code",
     preview: "Preview",
+    cancel: "Cancel",
+    save: "Save",
   },
 
   // Welcome
@@ -38,6 +42,7 @@ export const enUS: Translations = {
     copyToClipboard: "Copy to clipboard",
     copiedToClipboard: "Copied to clipboard",
     failedToCopyToClipboard: "Failed to copy to clipboard",
+    linkCopied: "Link copied to clipboard",
   },
 
   // Input Box

frontend/src/core/i18n/locales/types.ts

@@ -9,6 +9,8 @@ export interface Translations {
     home: string;
     settings: string;
     delete: string;
+    rename: string;
+    share: string;
     openInNewWindow: string;
     close: string;
     more: string;
@@ -22,6 +24,8 @@ export interface Translations {
     loading: string;
     code: string;
     preview: string;
+    cancel: string;
+    save: string;
   };
 
   // Welcome
@@ -35,6 +39,7 @@ export interface Translations {
     copyToClipboard: string;
     copiedToClipboard: string;
     failedToCopyToClipboard: string;
+    linkCopied: string;
   };
 
   // Input Box

frontend/src/core/i18n/locales/zh-CN.ts

@@ -11,6 +11,8 @@ export const zhCN: Translations = {
     home: "首页",
     settings: "设置",
     delete: "删除",
+    rename: "重命名",
+    share: "分享",
     openInNewWindow: "在新窗口打开",
     close: "关闭",
     more: "更多",
@@ -24,6 +26,8 @@ export const zhCN: Translations = {
     loading: "加载中...",
     code: "代码",
     preview: "预览",
+    cancel: "取消",
+    save: "保存",
   },
 
   // Welcome
@@ -38,6 +42,7 @@ export const zhCN: Translations = {
     copyToClipboard: "复制到剪贴板",
     copiedToClipboard: "已复制到剪贴板",
     failedToCopyToClipboard: "复制到剪贴板失败",
+    linkCopied: "链接已复制到剪贴板",
   },
 
   // Input Box