feat(frontend): restyle monitoring charts on the Beszel school

Ports Beszel's chart design language onto our recharts primitives:
titled card grid, area fills on a true time axis, unit-aware Y ticks,
sorted dotted tooltips, and legend chips. System detail gains stacked
per-container Docker CPU/memory, per-sensor temperature lines, load
1/5/15, and GPU usage/VRAM — all from data the agent already sends.

Generated with [Devin](https://devin.ai)

Co-Authored-By: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>

apps/frontend/src/index.css

@@ -25,6 +25,16 @@
   --icon-bg: #1c1c1e;
   --popover: #141414;
 
+  /* chart series palette (monitoring graphs) */
+  --chart-1: #3b82f6;
+  --chart-2: #10b981;
+  --chart-3: #8b5cf6;
+  --chart-4: #f59e0b;
+  --chart-5: #22d3ee;
+  --chart-6: #fb7185;
+  --chart-7: #a3e635;
+  --chart-8: #c084fc;
+
   --background: var(--bg);
   --foreground: var(--text);
   --card: var(--surface);
@@ -57,6 +67,16 @@
   --icon-bg: #f4f4f5;
   --popover: #ffffff;
 
+  /* chart series palette (monitoring graphs) — darker for light bg */
+  --chart-1: #2563eb;
+  --chart-2: #059669;
+  --chart-3: #7c3aed;
+  --chart-4: #d97706;
+  --chart-5: #0891b2;
+  --chart-6: #e11d48;
+  --chart-7: #65a30d;
+  --chart-8: #9333ea;
+
   --background: var(--bg);
   --foreground: var(--text);
   --card: var(--surface);