feat(design): foundation pass — dusty violet palette, warm parchment light, Inter + JetBrains Mono

Applies the FabledSword + Scribe iteration palette to theme.css end to
end: indigo (#7c3aed) → dusty violet (#5B4A8A) accent, cool grey →
Obsidian/Iron/Pewter dark surfaces, warm parchment (#F5F1E8) light
mode, Inter body + JetBrains Mono code loaded alongside Fraunces, and
neutral hairline scrollbars (chrome is structural, not branded).

Adds the action token set (--color-action-primary Moss,
--color-action-secondary Bronze, --color-action-destructive Oxblood,
--color-action-ghost-border Pewter) but does not yet reclassify any
buttons — surface-phase work. Buttons remain dusty-violet gradients in
the meantime, by design.

Removes deprecated --color-accent-warm; replaces concrete usages with
--color-text-secondary (dates, flavor copy) or --color-warning (paused
status). Sweeps hardcoded indigo literals in component scoped CSS so
they don't bypass the token system.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

frontend/src/components/EventSlideOver.vue

@@ -315,7 +315,7 @@ async function doDelete() {
             <label class="so-label so-label-inline">Color</label>
             <div class="color-row">
               <input v-model="color" type="color" class="color-picker" title="Pick event color" />
-              <input v-model="color" class="so-input color-hex" placeholder="#7c3aed" />
+              <input v-model="color" class="so-input color-hex" placeholder="#5B4A8A" />
               <button v-if="color" type="button" class="btn-clear-color" @click="color = ''">✕</button>
             </div>
           </div>
@@ -450,7 +450,7 @@ async function doDelete() {
 .so-past-hint {
   margin: 4px 0 0;
   font-size: 0.75rem;
-  color: var(--color-accent-warm, #d4a017);
+  color: var(--color-text-secondary);
   font-style: italic;
 }