fix: resolve QG-001 typography token drift and QG-006 style violations

Replace raw line-height values with --leading-none/--leading-loose
design tokens in 3 CSS files. Fix 7 PHP style issues: import ordering,
unused imports, brace placement, multi-line argument formatting.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

web/css/components/app-tabs.css

@@ -47,7 +47,7 @@
     background: transparent;
     color: var(--tabs-muted);
     font-size: var(--text-xs);
-    line-height: 1;
+    line-height: var(--leading-none);
     width: 24px;
     height: 24px;
     padding: 0;