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/components/ResourcesView.tsx

@@ -634,7 +634,7 @@ export default function ResourcesView() {
                 defaultValue="images"
                 className="flex-1 flex flex-col w-full rounded-lg border bg-card shadow-card-bevel overflow-hidden min-h-[400px] animate-in fade-in-0 slide-in-from-bottom-2 duration-300 delay-150"
             >
-                <div className="px-4 pt-3 pb-0 border-b border-glass-border bg-glass">
+                <div className="px-4 pt-3 pb-2">
                     <TabsList className="grid grid-cols-4 w-full md:w-[680px] h-9 gap-1 p-0">
                         <TabsHighlight className="rounded-md bg-glass-highlight" transition={springs.snappy}>
                             {(['images', 'volumes', 'networks'] as const).map(tab => (