feat(themes): add catppuccin mocha, nord, and dracula themes

Community-standard palettes mapped to nib's 18-token design system.
Theme cycle extended: dark → paper → tinycard → catppuccin → nord → dracula.

web/style.css

@@ -74,6 +74,72 @@
     --mono: 'JetBrains Mono', ui-monospace, monospace;
 }
 
+[data-theme="catppuccin"] {
+    color-scheme: dark;
+    --bg: #1e1e2e;
+    --surf: #181825;
+    --raised: #313244;
+    --border: #45475a;
+    --soft: #252536;
+    --text: #cdd6f4;
+    --muted: #a6adc8;
+    --dim: #6c7086;
+    --accent: #cba6f7;
+    --a-bg: rgba(203,166,247,.09);
+    --a-str: rgba(203,166,247,.22);
+    --todo: #f9e2af;
+    --note: #94e2d5;
+    --event: #89b4fa;
+    --remind: #fab387;
+    --ok: #a6e3a1;
+    --danger: #f38ba8;
+    --lineage: #f5c2e7;
+}
+
+[data-theme="nord"] {
+    color-scheme: dark;
+    --bg: #2e3440;
+    --surf: #3b4252;
+    --raised: #434c5e;
+    --border: #4c566a;
+    --soft: #363d4a;
+    --text: #eceff4;
+    --muted: #d8dee9;
+    --dim: #4c566a;
+    --accent: #88c0d0;
+    --a-bg: rgba(136,192,208,.09);
+    --a-str: rgba(136,192,208,.22);
+    --todo: #ebcb8b;
+    --note: #8fbcbb;
+    --event: #81a1c1;
+    --remind: #d08770;
+    --ok: #a3be8c;
+    --danger: #bf616a;
+    --lineage: #b48ead;
+}
+
+[data-theme="dracula"] {
+    color-scheme: dark;
+    --bg: #282a36;
+    --surf: #21222c;
+    --raised: #44475a;
+    --border: #6272a4;
+    --soft: #343746;
+    --text: #f8f8f2;
+    --muted: #bfbfbf;
+    --dim: #6272a4;
+    --accent: #bd93f9;
+    --a-bg: rgba(189,147,249,.09);
+    --a-str: rgba(189,147,249,.22);
+    --todo: #f1fa8c;
+    --note: #8be9fd;
+    --event: #8be9fd;
+    --remind: #ffb86c;
+    --ok: #50fa7b;
+    --danger: #ff5555;
+    --lineage: #ff79c6;
+}
+
 /* ── RESET ──────────────────────────────────────────── */
 *, *::before, *::after { margin: 0; padding: 0; box-sizing: border-box; }
 html, body { height: 100%; overflow: hidden; }