redesign: complete UI overhaul for 54 nodes and 26 projects

- Replace D3 force graph with categorized grid layout for topology
  (54 nodes organized by type: infrastructure, servers, PCs, etc.)
- Replace individual task cards with project summary cards
  (progress bars and stage chips instead of 1700+ task cards)
- Compact node cards with status-colored backgrounds
- Better calendar empty state with centered icon
- Refined dark theme with more color depth
- Remove D3 dependency (no longer needed)
- Fix text sizes for 4K TV readability at distance

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

frontend/src/index.css

@@ -1,16 +1,23 @@
 @import "tailwindcss";
 
 @theme {
-  --color-bg-primary: #0a0a0f;
-  --color-bg-secondary: #12121a;
-  --color-bg-card: #1a1a2e;
-  --color-border: #2a2a3e;
-  --color-text-primary: #e4e4e7;
-  --color-text-secondary: #a1a1aa;
-  --color-accent: #3b82f6;
-  --color-success: #22c55e;
-  --color-danger: #ef4444;
-  --color-warning: #f59e0b;
+  --color-bg-primary: #0b0d14;
+  --color-bg-secondary: #111520;
+  --color-bg-card: #181d2a;
+  --color-bg-card-hover: #1f2638;
+  --color-border: #252d3f;
+  --color-border-light: #2e3750;
+  --color-text-primary: #e8eaf0;
+  --color-text-secondary: #8892a8;
+  --color-text-muted: #5c6478;
+  --color-accent: #4f8ff7;
+  --color-accent-dim: #2a4a80;
+  --color-success: #34d399;
+  --color-success-dim: #0d3d2e;
+  --color-danger: #f87171;
+  --color-danger-dim: #3d1515;
+  --color-warning: #fbbf24;
+  --color-warning-dim: #3d2e0a;
 }
 
 html {
@@ -20,9 +27,21 @@ html {
 body {
   background-color: var(--color-bg-primary);
   color: var(--color-text-primary);
-  font-family: "Inter", system-ui, sans-serif;
+  font-family: "Inter", system-ui, -apple-system, sans-serif;
   margin: 0;
   overflow: hidden;
   width: 3840px;
   height: 2160px;
 }
+
+/* Smooth scrollbar for overflow areas */
+::-webkit-scrollbar {
+  width: 6px;
+}
+::-webkit-scrollbar-track {
+  background: transparent;
+}
+::-webkit-scrollbar-thumb {
+  background: var(--color-border);
+  border-radius: 3px;
+}