prod: UI Optimisée mise en production

- Documentation archivée et réorganisée
- Backend: Ajout tests, migrations, library service, rate limiting
- Frontend: Suppression Flutter, focus sur interface web HTML/JS
- Tailwind CSS ajouté pour le style
- Améliorations UX et corrections bugs

Generated with [Claude Code](https://claude.com/claude-code)
via [Happy](https://happy.engineering)

Co-Authored-By: Claude <noreply@anthropic.com>
Co-Authored-By: Happy <yesreply@happy.engineering>

backend/QUICK_START_MIGRATION.md

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+# Quick Start - Database Migration
+
+## Apply the Migration
+
+```bash
+cd /opt/audiOhm/backend
+
+# Option 1: Using the helper script
+./run_migration.sh upgrade
+
+# Option 2: Using Alembic directly
+alembic upgrade head
+```
+
+## Verify Migration Success
+
+```bash
+# Check current version
+./run_migration.sh current
+
+# Or using Alembic directly
+alembic current
+```
+
+## What Gets Created
+
+Two new tables will be created:
+
+1. **listening_history** - Track listening records for users
+2. **liked_tracks** - User's favorite/liked tracks
+
+## Need Help?
+
+```bash
+# Show all available commands
+./run_migration.sh help
+
+# Or read the full guide
+cat ALEMBIC_GUIDE.md
+```
+
+## Revert if Needed
+
+```bash
+# Revert the migration
+./run_migration.sh downgrade-1
+
+# Or using Alembic
+alembic downgrade -1
+```
+
+## Check Tables in Database
+
+```bash
+sudo -u postgres psql spotify_le_2
+\dt
+\q
+```
+
+## Important Notes
+
+- Make sure PostgreSQL is running before applying migration
+- The migration uses CASCADE deletes - deleting a user or track will automatically remove related history/likes
+- The `liked_tracks` table has a UNIQUE constraint to prevent duplicate likes
+- Both tables have optimized indexes for common queries
+
+## Status
+
+✅ Migration file created and validated
+✅ Ready to apply to database
+✅ Full downgrade support included
+✅ Documentation complete