feat(docker-watcher): phase 14 - frontend polish & modern UI

Design system with CSS custom properties (light/dark themes).
38 Lucide SVG icon components. Dark mode with system preference.
EN/RU localization with i18n store. Skeleton loaders, empty states,
toggle switches, micro-interactions. Responsive sidebar with
mobile hamburger menu. All pages polished with consistent styling.

web/src/app.css

@@ -1 +1,55 @@
 @import 'tailwindcss';
+@import '$lib/styles/tokens.css';
+
+/* ── Base Styles ──────────────────────────────────────────────────── */
+
+html {
+  font-family: var(--font-family-sans);
+  -webkit-font-smoothing: antialiased;
+  -moz-osx-font-smoothing: grayscale;
+}
+
+body {
+  background-color: var(--surface-page);
+  color: var(--text-primary);
+}
+
+/* Screen reader only helper */
+.sr-only {
+  position: absolute;
+  width: 1px;
+  height: 1px;
+  padding: 0;
+  margin: -1px;
+  overflow: hidden;
+  clip: rect(0, 0, 0, 0);
+  white-space: nowrap;
+  border-width: 0;
+}
+
+/* ── Focus Ring Utility ───────────────────────────────────────────── */
+
+.focus-ring:focus-visible {
+  outline: 2px solid var(--border-focus);
+  outline-offset: 2px;
+}
+
+/* ── Custom Scrollbar ─────────────────────────────────────────────── */
+
+::-webkit-scrollbar {
+  width: 6px;
+  height: 6px;
+}
+
+::-webkit-scrollbar-track {
+  background: transparent;
+}
+
+::-webkit-scrollbar-thumb {
+  background: var(--border-primary);
+  border-radius: var(--radius-full);
+}
+
+::-webkit-scrollbar-thumb:hover {
+  background: var(--text-tertiary);
+}