Proposed changes

This PR implements app-specific favicon and PWA icon functionality, allowing each Lowcoder application to have its own visual identity in browser tabs and when installed as a Progressive Web App (PWA).

Types of changes

What types of changes does your code introduce to Lowcoder?
Put an x in the boxes that apply.

• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation Update (if none of the other choices apply)

Checklist

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This is simply a reminder of what we are going to look for before merging your code.
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• Lint and unit tests pass locally with my changes
• I have added tests that prove my fix is effective or that my feature works
• I have added necessary documentation (if appropriate)
• Any dependent changes have been merged and published in downstream modules

✨ Features

Frontend Changes

• Per-App Favicon Injection: Each app route now injects app-specific favicon, apple-touch-icon, and PWA manifest links
• Smart Icon Handling: Uses app settings icon with fallback to branding logo or default assets
• PWA Meta Tags: Adds Open Graph, Twitter Card, and theme-color meta tags for each app
• Dynamic Icon Conversion: New utility functions for converting various icon formats to favicon-compatible formats
• Enhanced Icon Display: Improved MultiIconDisplay component with better error handling and icon parsing

Backend Changes

• App Icon Controller: New REST endpoint for serving app-specific icons with proper caching headers
• Security Updates: Enhanced security configuration to allow icon serving from authenticated routes
• Icon Processing: Server-side icon conversion and optimization for various formats

Documentation

• PWA Icons Guide: documentation for implementing app-specific icons and favicons
• Best Practices: Guidelines for icon formats, sizes, and PWA requirements

🔧 Console Error Fixes

During development, several console errors were identified and resolved:

• Icon Parsing Issues: Fixed icon identifier parsing in MultiIconDisplay component
• Missing Icon Definitions: Added proper error handling for missing FontAwesome and Ant Design icons
• Type Safety: Improved TypeScript types and error handling throughout icon-related components
• Performance: Optimized icon loading and caching mechanisms

📁 Files Modified

Core Feature Files

• client/packages/lowcoder/src/app.tsx - Removed global favicon, added per-route handling
• client/packages/lowcoder/src/pages/editor/editorView.tsx - Added app-specific favicon injection
• client/packages/lowcoder/src/pages/ApplicationV2/index.tsx - Added favicon handling for admin view
• client/packages/lowcoder/src/comps/comps/multiIconDisplay.tsx - Enhanced icon display and error handling
• client/packages/lowcoder/src/util/iconConversionUtils.ts - New utility for icon format conversion
• server/api-service/lowcoder-server/src/main/java/org/lowcoder/api/application/ApplicationController.java - Added icon serving endpoint
• server/api-service/lowcoder-server/src/main/java/org/lowcoder/api/framework/security/SecurityConfig.java - Updated security for icon access
• server/api-service/lowcoder-server/src/main/java/org/lowcoder/api/application/AppIconController.java - New icon controller
• docs/build-applications/app-editor/pwa-icons-and-favicons.md - New documentation

🚀 Benefits

1. Brand Consistency: Each app can maintain its unique visual identity
2. PWA Support: Proper icon handling for Progressive Web App installation
3. User Experience: Clear visual distinction between different applications
4. Developer Experience: Comprehensive documentation and utility functions
5. Error Resilience: Robust error handling prevents console errors

🧪 Testing

• Tested with various icon formats (PNG, SVG, FontAwesome, Ant Design)
• Verified PWA installation with app-specific icons
• Confirmed favicon changes across different browser tabs
• Tested fallback mechanisms for missing icons