feat(design): surface phase PR 7 — edge surfaces polish

Per the spec, the final per-surface PR bundles the smaller / chrome-y /
library-driven views (Header / Home / Calendar / Graph) together with
EventSlideOver since it's the calendar's primary interaction surface.

Button reclassification per Hybrid rule
- CalendarView btn-new-event: accent gradient → Moss action-primary.
  Creating an event is a workflow action, not a brand moment.
- EventSlideOver btn-primary (Save): accent gradient → Moss
- EventSlideOver btn-secondary (Cancel/No): muted ghost → Bronze
  action-secondary
- EventSlideOver btn-danger-ghost (Delete): hardcoded #ef4444 →
  --color-action-destructive ghost (with filled hover)
- EventSlideOver btn-danger (confirm Delete): hardcoded #ef4444 →
  --color-action-destructive filled

Brand-moment CTAs kept on accent
- HomeView btn-workspace-hero: home-page hero CTA into the active
  project — central brand-moment surface, gradient stays
- HomeView btn-workspace-sm: per-card workspace icon with the
  accent-tinted bg + hover-to-accent pattern, kept

Two-weights-only
- Snapped every font-weight 600/700 to 500 across the bundle
  (HomeView, GraphView, CalendarView, AppHeader, EventSlideOver).

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

frontend/src/views/GraphView.vue

@@ -759,7 +759,7 @@ onUnmounted(() => {
 
 .tooltip-title {
   font-size: 0.875rem;
-  font-weight: 600;
+  font-weight: 500;
   color: var(--color-text);
   margin-bottom: 0.25rem;
 }
@@ -821,7 +821,7 @@ onUnmounted(() => {
 
 .peek-type-badge {
   font-size: 0.68rem;
-  font-weight: 600;
+  font-weight: 500;
   text-transform: uppercase;
   letter-spacing: 0.05em;
   padding: 0.15rem 0.45rem;
@@ -860,7 +860,7 @@ onUnmounted(() => {
   margin: 0;
   padding: 0.75rem 0.75rem 0.4rem;
   font-size: 1rem;
-  font-weight: 600;
+  font-weight: 500;
   color: var(--color-text);
   flex-shrink: 0;
 }
@@ -898,7 +898,7 @@ onUnmounted(() => {
 
 .peek-linked-label {
   font-size: 0.7rem;
-  font-weight: 600;
+  font-weight: 500;
   text-transform: uppercase;
   letter-spacing: 0.05em;
   color: var(--color-text-muted);
@@ -933,7 +933,7 @@ onUnmounted(() => {
 
 .peek-linked-type {
   font-size: 0.65rem;
-  font-weight: 700;
+  font-weight: 500;
   width: 1.1rem;
   height: 1.1rem;
   border-radius: 50%;