palette tooltip: contextual description per lock state; earned date below Unlocked in green — TDD

- _palettes_for_user: shoptalk→description; "available by default" / "explore to unlock" / "recognized via {Title}"; unlocked_date key carries earned_at ISO for Note-unlocked
- template: data-shoptalk→data-description; data-unlocked-date now holds ISO datetime (was literal "Default")
- dashboard.js: lockText drops "— Default"; dateLine renders "Apr 22, 2026 · 3:05 AM" after Unlocked line
- _palette-picker.scss: tt-shoptalk→tt-description in display:block list; tt-date added
- _tooltips.scss: .tt-date mirrors .tt-expiry w. --priGn colour

Code architected by Disco DeDisco <discodedisco@outlook.com>
Git commit message Co-Authored-By:
Claude Sonnet 4.6 <noreply@anthropic.com>

src/static_src/scss/_tooltips.scss

@@ -10,6 +10,7 @@
     .tt-description { padding: 0.125rem; font-size: 0.75rem; }
     .tt-shoptalk    { font-size: 0.75rem; opacity: 0.75; }
     .tt-expiry      { font-size: 1rem; color: rgba(var(--priRd), 1); }
+    .tt-date        { font-size: 1rem; color: rgba(var(--priGn), 1); }
 }
 
 .token-tooltip,