v0.15.1: Backup page Részletek overhaul with per-drive tier sections

Replace Tároló section with collapsible Részletek containing 3 tiers:
- Tier 1: per-drive restic repo stats with storage labels
- Tier 2: cross-drive items grouped by destination, split by method
- Tier 3: remote backup placeholder
Restore UI now shows tier + drive labels in snapshot dropdown.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

controller/internal/web/templates/style.css

@@ -1600,6 +1600,65 @@ a.stat-card:hover {
     gap: .15rem;
 }
 
+/* Details tier (collapsible sections in Részletek) */
+.details-tier {
+    border-top: 1px solid var(--border-color);
+    margin-top: .5rem;
+}
+.details-tier:first-child {
+    border-top: none;
+    margin-top: 0;
+}
+.details-tier-header {
+    display: flex;
+    align-items: center;
+    gap: .5rem;
+    cursor: pointer;
+    padding: .5rem 0;
+    user-select: none;
+}
+.details-tier-header:hover {
+    opacity: .8;
+}
+.details-tier-header .expand-icon {
+    font-size: .7rem;
+    color: var(--text-muted);
+    min-width: 1rem;
+    text-align: center;
+}
+.details-tier-header .repo-tier-title {
+    margin-bottom: 0;
+}
+.details-tier-body {
+    padding-bottom: .75rem;
+}
+.drive-detail-card {
+    background: var(--bg-secondary);
+    border-radius: var(--radius);
+    padding: .75rem;
+    margin-bottom: .5rem;
+}
+.drive-detail-header {
+    font-size: .85rem;
+    font-weight: 600;
+    color: var(--text-primary);
+    margin-bottom: .5rem;
+}
+.method-group {
+    margin-top: .5rem;
+}
+.method-group-label {
+    font-size: .8rem;
+    font-weight: 600;
+    color: var(--text-secondary);
+    margin-bottom: .25rem;
+}
+.tier-empty-state {
+    font-size: .85rem;
+    color: var(--text-muted);
+    padding: .5rem 0;
+}
+
 .relative-time {
     color: var(--text-muted);
     font-size: .8rem;