style: comprehensive Light Mode overrides

Dashboard:
- Hero card: white glass (rgba 255,255,255,0.75) instead of dark glass
- Reduced shadows (no more extreme 40px shadow)
- LED digits: dark gold (#9A6500) with subtle shadow
- Countdown/tip badges: dark gold on light background
- Flag boxes: lighter shadows, no dark glow aura

MatchCards:
- LED time: dark gold for contrast on light bg
- Flag boxes: lighter shadows

BottomNav:
- White background with subtle top border
- Inactive tabs: darker for readability

Global:
- text-muted: 0.45 opacity (was 0.35) — better readability
- text-secondary: 0.65 (was 0.60)
- Gold: #B8740A (darker for light bg contrast)
- shadow-card: much lighter (was too heavy)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

frontend/src/index.css

@@ -46,20 +46,20 @@
   --bg-mid:         #E8EEF7;
   --surface-low:    #FFFFFF;
   --surface-mid:    #FFFFFF;
-  --surface-high:   #DDE5F0;
-  --border-subtle:  rgba(0,0,0,0.08);
+  --surface-high:   #E4EAF2;
+  --border-subtle:  rgba(0,0,0,0.1);
   --primary:        #1A8FE3;
   --primary-dim:    rgba(26,143,227,0.10);
-  --gold:           #D4880A;
-  --gold-glow:      rgba(212,136,10,0.3);
+  --gold:           #B8740A;
+  --gold-glow:      rgba(184,116,10,0.3);
   --cyan:           #0080C6;
   --text-primary:   #0D1526;
-  --text-secondary: rgba(13,21,38,0.6);
-  --text-muted:     rgba(13,21,38,0.35);
-  --success:        #1AAB72;
-  --error:          #D93025;
-  --shadow-card:    0 4px 20px rgba(0,0,0,0.12), 0 1px 4px rgba(0,0,0,0.08);
-  --card-shine:     rgba(255,255,255,0.85);
+  --text-secondary: rgba(13,21,38,0.65);
+  --text-muted:     rgba(13,21,38,0.45);
+  --success:        #168A5C;
+  --error:          #C92A1F;
+  --shadow-card:    0 2px 8px rgba(0,0,0,0.06), 0 1px 3px rgba(0,0,0,0.04);
+  --card-shine:     rgba(255,255,255,0.9);
   --scrollbar-bg:   var(--surface-high);
   --primary-rgb:    26, 143, 227;
 }