Restyle to light content theme with Lucide icons

- index.css: light body (#f4f5f7), white cards, sidebar stays dark navy
- AppIcon.tsx: Lucide icon lookup component for app tiles and nav
- Sidebar.tsx: Lucide nav icons (LayoutGrid, Users, Activity, LogOut)
- Dashboard.tsx: white cards with shadows, coloured Lucide app icons
- AdminMonitor.tsx: light theme throughout, Lucide tab icons,
  better status colours for light backgrounds

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

src/index.css

@@ -1,24 +1,37 @@
 *, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }
 
 :root {
-  --navy:       #1e3a5f;
-  --navy-dark:  #0f1f35;
-  --gold:       #c9a84c;
-  --gold-light: #e8c96d;
-  --surface:    #1a2d47;
-  --surface-2:  #243d5c;
-  --text:       #e8edf2;
-  --text-muted: #8ba3bc;
-  --danger:     #e05252;
-  --sidebar-w:  220px;
+  /* ── Sidebar / shell chrome (stays dark) ── */
+  --navy:        #1a1a2e;
+  --navy-dark:   #0f0f20;
+  --gold:        #c9a84c;
+  --gold-light:  #e8c96d;
+  --surface:     rgba(255,255,255,0.07);
+  --surface-2:   rgba(255,255,255,0.08);
+  --text:        rgba(255,255,255,0.88);
+  --text-muted:  rgba(255,255,255,0.48);
+
+  /* ── Content area (light) ── */
+  --body-bg:     #f4f5f7;
+  --card-bg:     #ffffff;
+  --card-border: #e4e8ee;
+  --text-dark:   #1e293b;
+  --text-mid:    #64748b;
+  --shadow-sm:   0 1px 3px rgba(0,0,0,0.07), 0 1px 2px rgba(0,0,0,0.04);
+  --shadow-md:   0 4px 12px rgba(0,0,0,0.08);
+
+  /* ── Shared ── */
+  --danger:      #dc2626;
+  --sidebar-w:   220px;
+  --radius:      10px;
   --font: -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
 }
 
 html, body, #root { height: 100%; }
 
 body {
-  background: var(--navy-dark);
-  color: var(--text);
+  background: var(--body-bg);
+  color: var(--text-dark);
   font-family: var(--font);
 }