feat(ui): redesign the overview page as a trend-first command deck

Replace the ten-small-cards overview with an action bar, four vitals
tiles carrying 72-sample sparklines seeded from /server/history, a
two-series throughput chart, a TCP/UDP connections chart, and a
grouped system strip (uptime xray|os, panel ram|threads, ip
addresses). StatusCard and XrayStatusCard are deleted; every modal
stays reachable from the action bar, the Xray error message moves
into a tooltip on the state pill, and the panel version text keeps
opening the update modal (the dev-channel switch lives there) even
when no update is available. Live values sit beside the
upload/download and tcp/udp legends, a health sentence appears only
when a vital crosses the shared warn/crit thresholds now exported
from models/status, and load average is left to System History.

The sidebar becomes an auto-collapsed 72px icon rail that expands as
an overlay on hover: rail width, brand-row height and menu paddings
are pinned so nothing shifts during the transition, the collapsed-menu
tooltips are disabled, hover state survives the per-page sidebar
remounts (with a matches(':hover') resync), and the manual collapse
trigger is gone.

Sparkline gains rgb()/rgba() support in its fill gradient, a
showLegend prop so pages stop reaching into its internals, and loses
a dependency-less repaint effect that doubled canvas paints. Chart
tooltips show clock time via the new TimeFormatter.formatClock;
accents come from theme tokens instead of status.cpu.color. Verified
by screenshot at 390/800/1150/1280/1400/1600px in light and dark,
en and fa-IR, plus programmatic geometry checks on the sidebar.
Locale files gain 8 keys and lose 9 dead ones across all 13
languages.

frontend/src/models/status.ts

@@ -1,5 +1,10 @@
 import { NumberFormatter } from '@/utils';
 
+export const USAGE_WARN_PERCENT = 80;
+export const USAGE_CRIT_PERCENT = 90;
+export const USAGE_WARN_COLOR = '#faad14';
+export const USAGE_CRIT_COLOR = '#ff4d4f';
+
 export class CurTotal {
   current: number;
   total: number;
@@ -16,9 +21,9 @@ export class CurTotal {
 
   get color(): string {
     const p = this.percent;
-    if (p < 80) return '#1677ff';
-    if (p < 90) return '#faad14';
-    return '#ff4d4f';
+    if (p < USAGE_WARN_PERCENT) return '#1677ff';
+    if (p < USAGE_CRIT_PERCENT) return USAGE_WARN_COLOR;
+    return USAGE_CRIT_COLOR;
   }
 }