Refactor admin panel and add migration documentation

- Add comprehensive migration guides (DEPLOYMENT_MIGRATION.md, DIRECTORY_STRUCTURE.md, MIGRATION_CHECKLIST.md)
- Refactor admin panel: split add.php, create reusable header/footer
- Update styles: admin.css, common.css, main.css
- Improve public pages: index.php, memoire.php
- Reorganize database documentation into database/docs/
- Update .gitignore and justfile

This prepares for migration to public/ directory structure

justfile

@@ -65,6 +65,7 @@ deploy:
     @echo ""
     @echo "Deploying public site..."
     rsync -vur --progress \
+        --chown="root:posterg" \
         --exclude 'vendor' \
         --exclude 'tests' \
         --exclude 'test.db' \
@@ -72,8 +73,8 @@ deploy:
         --exclude 'cache' \
         --exclude '*.md' \
         --exclude '.git*' \
+        --exclude '.jj' \
         --exclude '.DS_Store' \
-        --exclude 'admin' \
         --exclude 'database' \
         --exclude 'nginx' \
         --exclude 'docs' \
@@ -82,17 +83,6 @@ deploy:
         --exclude 'setup-dev.sh' \
         ./ posterg:/var/www/html/
     @echo ""
-    @echo "Deploying admin panel..."
-    rsync -vur --progress \
-        --exclude 'test.db' \
-        --exclude '*.db' \
-        --exclude 'cache' \
-        --exclude '*.md' \
-        ./admin/ posterg:/var/www/html/admin/
-    @echo ""
-    @echo "Deploying shared libraries..."
-    rsync -vur --progress --exclude 'test.db' ./lib/ posterg:/var/www/html/lib/
-    @echo ""
     @echo "Fixing permissions..."
     ssh posterg "chgrp -R posterg /var/www/html/inc /var/www/html/lib && \
                  chmod 755 /var/www/html/inc && chmod 644 /var/www/html/inc/* && \
@@ -105,6 +95,15 @@ deploy:
     @echo "  • Public: https://posterg.erg.be/"
     @echo "  • Admin:  https://posterg.erg.be/admin/"
 
+[group('deploy')]
+test-deploy:
+    @echo "⚠️  Deploying test database (will overwrite remote test.db)"
+    @echo "Creating database directory if needed..."
+    ssh posterg "mkdir -p /var/www/html/database"
+    rsync -vur --progress ./database/test.db posterg:/var/www/html/database/test.db
+    @echo "Setting correct permissions..."
+    ssh posterg "chgrp posterg /var/www/html/database /var/www/html/database/test.db && chmod 775 /var/www/html/database && chmod 660 /var/www/html/database/test.db"
+    @echo "✅ Test database deployed and configured"
 # ============================================================================
 # Testing
 # ============================================================================