[Feat] Comment reply notifications and chat page & sharing improvements

[CREDO23]

Description

• Add comment reply notifications (backend handler + frontend support)
• Rename Mentions tab to Comments with speech bubble icon
• Fix duplicate notifications and inbox count
• Remove branch picker; restrict edit/reload to last message only
• Improve public sharing discoverability
• Add clipboard utility with fallback and show selectable URLs in public links

Change Type

• Bug fix
• New feature
• Performance improvement
• Refactoring
• Documentation
• Dependency/Build system
• Breaking change
• Other (specify):

Testing Performed

• Tested locally
• Manual/QA verification

Checklist

• Follows project coding standards and conventions
• Documentation updated as needed
• Dependencies updated as needed
• No lint/build errors or new warnings
• All relevant tests are passing

High-level PR Summary

This PR enhances the chat commenting and notification system by introducing comment reply notifications that notify thread participants when someone replies. The Mentions tab has been renamed to Comments with a speech bubble icon to better reflect its expanded purpose. The notification system was refactored to fix duplicate notifications and correct inbox count calculations. Chat UI improvements include removing the branch picker component, restricting the edit button to only the last user message, and restricting the regenerate button to only the last assistant message. Public sharing functionality was improved by adding a globe indicator when public snapshots exist, showing selectable URLs in public link rows, relaxing permissions to view (not just create) public share links, and extracting a reusable clipboard utility with fallback support for non-secure contexts. Additional UI polish includes formatting improvements to the theme toggle component.

⏱️ Estimated Review Time: 30-90 minutes

💡 Review Order Suggestion

Order	File Path
1	surfsense_web/contracts/types/inbox.types.ts
2	surfsense_backend/app/services/notification_service.py
3	surfsense_backend/app/services/chat_comments_service.py
4	surfsense_web/hooks/use-api-key.ts
5	surfsense_web/lib/utils.ts
6	surfsense_web/components/layout/providers/LayoutDataProvider.tsx
7	surfsense_web/components/layout/ui/sidebar/InboxSidebar.tsx
8	surfsense_web/messages/en.json
9	surfsense_web/messages/zh.json
10	surfsense_web/components/assistant-ui/branch-picker.tsx
11	surfsense_web/components/assistant-ui/assistant-message.tsx
12	surfsense_web/components/assistant-ui/user-message.tsx
13	surfsense_backend/app/services/public_chat_service.py
14	surfsense_web/components/new-chat/chat-share-button.tsx
15	surfsense_web/components/public-chat-snapshots/public-chat-snapshot-row.tsx
16	surfsense_web/components/theme/theme-toggle.tsx

⚠️ Inconsistent Changes Detected

File Path	Warning
surfsense_web/components/theme/theme-toggle.tsx	This file contains only code formatting changes (whitespace/indentation) that appear unrelated to the main PR goals of comment reply notifications, chat page improvements, and sharing enhancements

[vercel]

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[recurseml]

Review by RecurseML

🔍 Review performed on 8c60910..1cf7205

✨ No bugs found, your code is sparkling clean

✅ Files analyzed, no issues (16)

• surfsense_backend/app/services/chat_comments_service.py
• surfsense_backend/app/services/notification_service.py
• surfsense_backend/app/services/public_chat_service.py
• surfsense_web/components/assistant-ui/assistant-message.tsx
• surfsense_web/components/assistant-ui/branch-picker.tsx
• surfsense_web/components/assistant-ui/user-message.tsx
• surfsense_web/components/layout/providers/LayoutDataProvider.tsx
• surfsense_web/components/layout/ui/sidebar/InboxSidebar.tsx
• surfsense_web/components/new-chat/chat-share-button.tsx
• surfsense_web/components/public-chat-snapshots/public-chat-snapshot-row.tsx
• surfsense_web/components/theme/theme-toggle.tsx
• surfsense_web/contracts/types/inbox.types.ts
• surfsense_web/hooks/use-api-key.ts
• surfsense_web/lib/utils.ts
• surfsense_web/messages/en.json
• surfsense_web/messages/zh.json