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/AuditLogView.tsx

@@ -123,9 +123,9 @@ export function AuditLogView() {
                             <CardTitle>Audit Log</CardTitle>
                         </div>
                         <div className="flex items-center gap-2">
-                            <DropdownMenu>
+                            <DropdownMenu modal={false}>
                                 <DropdownMenuTrigger asChild>
-                                    <Button variant="outline" size="sm">
+                                    <Button variant="outline" size="sm" className="border-border">
                                         <Download className="w-4 h-4 mr-2" />
                                         Export
                                         <ChevronDown className="w-3 h-3 ml-1" />
@@ -136,7 +136,7 @@ export function AuditLogView() {
                                     <DropdownMenuItem onClick={() => handleExport('json')}>Export as JSON</DropdownMenuItem>
                                 </DropdownMenuContent>
                             </DropdownMenu>
-                            <Button variant="outline" size="sm" onClick={fetchLogs} disabled={loading}>
+                            <Button variant="outline" size="sm" className="border-border" onClick={fetchLogs} disabled={loading}>
                                 <RefreshCw className={`w-4 h-4 mr-2 ${loading ? 'animate-spin' : ''}`} />
                                 Refresh
                             </Button>