refactor: implement minimal PWA caching strategy

- Cache only essential PWA assets (manifest, icons, core scripts)
- Use Network First for all other requests
- Remove aggressive caching of UI components and styles
- Preserve PWA installation while minimizing cache footprint

src/styles/components.css

@@ -349,35 +349,6 @@ button i {
     margin-right: 0.5rem;
 }
 
-/* Pay-per-session UI - Обновленный трехцветный таймер */
-.session-timer {
-    padding: 8px 16px;
-    border-radius: 8px;
-    font-weight: 600;
-    font-size: 14px;
-    display: flex;
-    align-items: center;
-    gap: 8px;
-    border: 1px solid rgba(255, 255, 255, 0.1);
-    backdrop-filter: blur(10px);
-    transition: all 0.5s ease;
-}
-
-.session-timer:hover {
-    transform: translateY(-1px);
-    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.2);
-}
-
-/* Анимация пульсации для красной зоны */
-@keyframes timer-pulse {
-    0%, 100% { opacity: 1; }
-    50% { opacity: 0.7; }
-}
-
-.session-timer.animate-pulse {
-    animation: timer-pulse 2s ease-in-out infinite;
-}
-
 /* Lightning button */
 .lightning-button {
     background: linear-gradient(135deg, #f59e0b 0%, #d97706 100%);