feat: implement design system — domain colors, date typography, interaction states, CV family colors

Apply the collaboratively-written design system from .interface-design/system.md:

- Domain color map: Social pages (rose), Code pages (emerald), Reading pages
  (orange), Music pages (purple) replace generic accent tokens
- Font-mono on all <time> elements via global CSS rule + wrap 7 non-<time> dates
- Shadow standardization: replace hover:shadow-lg with border-hover on news cards
- Active states: scale(0.97) press feedback on buttons and pagination links
- Gradient cleanup: remove to-white gradient on github featured project cards
- CV Skills & Interests: cycle through 8 distinct colors per family category
  (amber, emerald, sky, rose, purple, orange, teal, indigo) on both CV page
  and homepage
- Update system.md with refined palette documentation and domain color spec

Files: 19 changed across templates, CSS, and design documentation

Confab-Link: http://localhost:8080/sessions/bd3f7012-c703-47e9-bfe2-2ad04ce1842d

css/tailwind.css

@@ -466,6 +466,14 @@
   }
 }
 
+/* Active states — subtle press feedback on buttons */
+@layer base {
+  button:active:not(:disabled),
+  .pagination-link:active:not(.disabled) {
+    transform: scale(0.97);
+  }
+}
+
 /* Video embeds */
 @layer components {
   .video-embed {
@@ -520,6 +528,13 @@
   }
 }
 
+/* Dates — monospace for technical texture (system.md: every <time> gets font-mono) */
+@layer base {
+  time {
+    font-family: ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, "Liberation Mono", "Courier New", monospace;
+  }
+}
+
 /* Apply content-visibility to images and post items for performance */
 @layer base {
   /* Responsive typography */