refactor(ui): single global .fc-muted token (DRY pattern sweep)

The muted-text token was redefined identically in 12 component <style scoped>
blocks. Consolidate to one global utility in styles/app.css; remove the 12
copies. Keeps the explicit on-surface-variant (vellum) token, NOT Vuetify's
opacity-based text-medium-emphasis (per the muted-text-token rule). Behavior-
preserving: every class=fc-muted usage now resolves to the single source.

§8b exhaustiveness caught (and I fixed) my own sed clobbering the new app.css
rule — now exactly one .fc-muted definition exists, zero component-local.
Catalog updated.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

frontend/src/styles/app.css

@@ -31,3 +31,11 @@
   border: 1px solid rgb(var(--v-theme-on-surface-variant) / 0.25);
   box-shadow: 0 2px 8px rgba(0, 0, 0, 0.4);
 }
+
+/* Canonical muted/secondary text token (DRY pattern sweep 2026-06-09).
+   Was redefined identically in 12 component <style scoped> blocks; now one
+   global utility. Muted text uses the explicit on-surface-variant (vellum)
+   token, NOT opacity — Vuetify's text-medium-emphasis is opacity-based and is
+   deliberately not used here. `.fc-muted` is a custom class Vuetify never
+   emits, so no specificity/reorder fight — no !important needed. */
+.fc-muted { color: rgb(var(--v-theme-on-surface-variant)); }