feat: upgrade to Tailwind CSS v4 and update all dependencies

[CorentinLumineau]

• Migrated from Tailwind CSS v3 to v4 with CSS-based configuration
• Updated all dependencies to latest stable versions
• Upgraded pnpm from 10.10.1 to 10.18.3
• Updated globals.css to use new @import "tailwindcss" syntax
• Moved theme configuration to @theme directive in CSS
• Updated PostCSS config to use @tailwindcss/postcss plugin
• Simplified Tailwind config files (removed tailwindcss-animate plugin)
• Updated apps/web to use Tailwind v4
• Updated packages/config with Tailwind v4 dependencies
• Added make verify command to run tests, lint, type-check, and build

Breaking changes:

• Removed tailwindcss-animate package (animations now in CSS @theme)
• Updated date-fns from ^3.6.0 to ^4.1.0
• PostCSS configuration now uses @tailwindcss/postcss instead of tailwindcss

🤖 Generated with Claude Code

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Project	Deployment	Preview	Comments	Updated (UTC)
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[claude]

Claude finished @CorentinLumineau's task —— View job

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PR Review: Tailwind CSS v4 Migration

I've completed a comprehensive review of this Tailwind CSS v4 migration. Here's my detailed feedback:

Review Checklist:

• Read CLAUDE.md for repository guidelines
• Review Tailwind CSS v4 migration approach
• Examine configuration changes (postcss, tailwind configs)
• Check CSS changes in globals.css
• Verify Makefile additions
• Review dependency updates and potential breaking changes
• Assess security and performance implications
• Check for missing documentation updates
• Provide comprehensive review feedback

✅ Strengths

Excellent Migration Approach

• Proper CSS-first approach: Correctly uses @import "tailwindcss" and @theme {} directive in /apps/web/app/globals.css:1-36
• Animation migration: Successfully moved from tailwindcss-animate plugin to CSS-based animations in @theme block
• PostCSS update: Properly updated to use @tailwindcss/postcss plugin in /apps/web/postcss.config.mjs:4
• Workspace consistency: Both main and shared configs updated appropriately

Dependency Management

• PNPM upgrade: Updated from 10.10.1 to 10.18.3 (good for performance and security)
• Comprehensive updates: All dependencies properly updated to latest stable versions
• Breaking change handling: date-fns v4 upgrade properly managed

Build Tooling Improvements

• New verification command: Added make verify command in /Makefile:149-159 for comprehensive testing pipeline
• Better workflow: Combines tests, linting, type-check, and build in logical sequence

⚠️ Issues & Recommendations

1. CRITICAL: Configuration Inconsistency

Location: /apps/web/tailwind.config.ts vs /packages/config/tailwind.config.js

Problem: The configs have diverged - the shared config includes zIndex extensions (/packages/config/tailwind.config.js:55-61) that aren't in the web app config.

Fix: Ensure consistent configuration:

// apps/web/tailwind.config.ts
theme: {
  extend: {
+   zIndex: {
+     '60': '60',
+     '70': '70', 
+     '80': '80',
+     '90': '90',
+     '100': '100',
+   },
    borderRadius: {

2. MEDIUM: CSS Variable Duplication

Location: /apps/web/app/globals.css:38-82

Problem: Hardcoded theme variables in CSS conflict with dynamic theme system in /apps/web/app/lib/theme/index.ts:44-69

Recommendation: Remove hardcoded CSS variables and rely entirely on JavaScript theme system for consistency.

3. MEDIUM: PNPM Version Mismatch

Location: CLAUDE.md:55 vs package.json:3

Problem: Documentation says pnpm@10.10.0 but package.json uses 10.18.3

Fix: Update CLAUDE.md documentation to reflect actual version.

4. LOW: Missing Documentation Updates

Problem: CLAUDE.md still references Tailwind v3 patterns and doesn't mention v4 migration

Recommendation: Update architecture documentation to reflect new CSS-based configuration approach.

🚀 Performance & Security Assessment

Performance Impact

• ✅ Positive: Tailwind v4 has smaller runtime and better CSS output
• ✅ Build optimization: @tailwindcss/postcss plugin more efficient than v3
• ✅ Animation performance: CSS-based animations in @theme are more performant

Security

• ✅ Dependencies: All updates appear to be legitimate stability/security improvements
• ✅ No security regressions: date-fns v4 includes security fixes
• ✅ PNPM lockfile: Properly updated with integrity checks

📝 Required Actions Before Merge

High Priority

1. Fix zIndex configuration mismatch between web app and shared config
2. Test theme switching functionality to ensure dynamic theming still works with new CSS structure
3. Run the new make verify command to ensure all checks pass

Medium Priority

4. Update CLAUDE.md documentation for Tailwind v4 patterns
5. Consider removing hardcoded CSS variables in favor of pure JavaScript theme system

Testing Recommendations

# Essential pre-merge testing
make verify                    # Run full test suite
pnpm dev                      # Test development server  
# Test theme switching in browser
# Test dark/light mode toggle
# Test responsive breakpoints

🎯 Overall Assessment

Score: 8.5/10 - This is a very well-executed Tailwind v4 migration with modern best practices. The few issues identified are fixable and don't block the core functionality.

Recommendation: Approve with minor fixes - Address the configuration inconsistency and test thoroughly before merging.

The migration properly follows Tailwind v4 patterns and maintains backward compatibility with the existing theme system. Great work on the comprehensive dependency updates and improved build tooling!

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Bug: CSS Variable Redundancy Causes Theme Override

The --radius CSS variable is defined redundantly in globals.css, appearing in both the @theme and :root blocks. The :root definition overrides the @theme one, making the latter ineffective.