feat: UI polish sprint — 7 items + logs toolbar redesign (#365)

* feat: UI polish sprint — tag filters, toast tokens, logs toolbar, billing portal, editor UX

- Fleet: replace inline tag pills with multi-select combobox dropdown
- Toast: remap all notification colors to oklch design tokens
- Logs: convert floating hover toolbar to permanent pinned toolbar,
  replace all hardcoded colors with design tokens for theme support
- Audit: fix dropdown scroll-lock (modal=false), light theme button contrast
- Resources: remove redundant inner border/bg on tab wrapper
- Editor: add ⌘K/Ctrl+K shortcut hint and handler, standardize button heights
- Billing: signed Lemon Squeezy portal URLs via sencho.io proxy for all tiers
- New MultiSelectCombobox UI component

* feat(editor): replace button row with split-button dropdown

Replace three separate editor buttons (Discard, Save Only, Save & Deploy)
with a compact split-button dropdown. Primary action is "Save & Deploy";
chevron opens dropdown with "Save Only" and "Discard Changes" options.

frontend/src/index.css

@@ -48,6 +48,7 @@
   --info: oklch(0.62 0.14 250);
   --info-foreground: oklch(1 0 0);
   --info-muted: oklch(0.62 0.14 250 / 0.12);
+  --destructive-muted: oklch(0.63 0.19 23 / 0.12);
 
   /* Charts */
   --chart-1: oklch(0.8100 0.1700 75.3500);
@@ -187,6 +188,7 @@
   --info: oklch(0.70 0.14 250);
   --info-foreground: oklch(0.10 0 0);
   --info-muted: oklch(0.70 0.14 250 / 0.15);
+  --destructive-muted: oklch(0.69 0.20 24 / 0.15);
 
   /* Charts — monochrome blue/teal */
   --chart-1: oklch(0.72 0.08 220);
@@ -336,6 +338,7 @@
   --color-info: var(--info);
   --color-info-foreground: var(--info-foreground);
   --color-info-muted: var(--info-muted);
+  --color-destructive-muted: var(--destructive-muted);
 
   --font-sans: var(--font-sans);
   --font-mono: var(--font-mono);