feat(phase3): import/export, sparklines, user theme overrides

- JSON import/export with conflict resolution (skip/overwrite) + admin UI
- Ping history sparklines on AppWidget and AppCard (24h, 288 points)
- Hourly cleanup job for old AppStatus records
- User theme preferences (hue, saturation, mode, background, locale)
- Settings page with ThemeCustomizer (sliders, toggles, live preview)
- Prisma migration for user preference fields
- i18n translations for all new strings (EN/RU)

src/lib/components/layout/Header.svelte

@@ -161,6 +161,27 @@
 						<p class="truncate text-xs text-muted-foreground">{user.email}</p>
 					</div>
 
+					<a
+						href="/settings"
+						onclick={() => (showUserMenu = false)}
+						class="flex w-full items-center gap-2 rounded-sm px-3 py-1.5 text-sm text-popover-foreground transition-colors hover:bg-accent"
+					>
+						<svg
+							class="h-4 w-4"
+							xmlns="http://www.w3.org/2000/svg"
+							viewBox="0 0 24 24"
+							fill="none"
+							stroke="currentColor"
+							stroke-width="2"
+							stroke-linecap="round"
+							stroke-linejoin="round"
+						>
+							<path d="M12.22 2h-.44a2 2 0 0 0-2 2v.18a2 2 0 0 1-1 1.73l-.43.25a2 2 0 0 1-2 0l-.15-.08a2 2 0 0 0-2.73.73l-.22.38a2 2 0 0 0 .73 2.73l.15.1a2 2 0 0 1 1 1.72v.51a2 2 0 0 1-1 1.74l-.15.09a2 2 0 0 0-.73 2.73l.22.38a2 2 0 0 0 2.73.73l.15-.08a2 2 0 0 1 2 0l.43.25a2 2 0 0 1 1 1.73V20a2 2 0 0 0 2 2h.44a2 2 0 0 0 2-2v-.18a2 2 0 0 1 1-1.73l.43-.25a2 2 0 0 1 2 0l.15.08a2 2 0 0 0 2.73-.73l.22-.39a2 2 0 0 0-.73-2.73l-.15-.08a2 2 0 0 1-1-1.74v-.5a2 2 0 0 1 1-1.74l.15-.09a2 2 0 0 0 .73-2.73l-.22-.38a2 2 0 0 0-2.73-.73l-.15.08a2 2 0 0 1-2 0l-.43-.25a2 2 0 0 1-1-1.73V4a2 2 0 0 0-2-2z" />
+							<circle cx="12" cy="12" r="3" />
+						</svg>
+						{$t('settings.title')}
+					</a>
+
 					<form method="POST" action="/auth/logout">
 						<button
 							type="submit"