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/views/ChatView.vue

@@ -520,7 +520,7 @@ onUnmounted(() => {
 .btn-new-conv--full { width: 100%; }
 .btn-new-conv:hover {
   opacity: 0.9;
-  box-shadow: 0 0 14px rgba(129, 140, 248, 0.35);
+  box-shadow: 0 0 14px rgba(91, 74, 138, 0.35);
 }
 
 .sidebar-search-row {
@@ -612,7 +612,7 @@ onUnmounted(() => {
   border-left: 3px solid transparent;
   transition: background 0.15s, border-color 0.15s;
 }
-.conv-item:hover { background: rgba(99,102,241,0.05); border-left-color: var(--color-primary); }
+.conv-item:hover { background: rgba(91, 74, 138,0.05); border-left-color: var(--color-primary); }
 .conv-item.active {
   background: color-mix(in srgb, var(--color-primary) 15%, transparent);
   color: var(--color-primary);
@@ -704,7 +704,7 @@ onUnmounted(() => {
   50% {
     border-color: var(--color-primary);
     color: var(--color-primary);
-    box-shadow: 0 0 6px rgba(99, 102, 241, 0.4);
+    box-shadow: 0 0 6px rgba(91, 74, 138, 0.4);
   }
 }
 .scope-dot { font-size: 0.6rem; }