Polish Foundry desktop UI: billing redesign, sidebar hover menu, org switching fix

- Redesign billing page with task-hours pricing model (Free: 8h, Pro: 200h/seat)
- Add bulk hour purchase packages and Stripe payment management
- Remove Usage nav section, add upgrade CTA in Members for free plan
- Fix gear icon to open menu on hover with debounced timers
- Fix org switching in workspace flyout (portal outside-click detection)
- Fix tab strip padding when sidebar is collapsed
- Update website components and Tauri config

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

frontend/packages/website/src/components/DownloadFoundry.tsx

@@ -105,7 +105,7 @@ export function DownloadFoundry() {
             </button>
 
             {showDropdown && (
-              <div className="absolute left-1/2 top-full mt-2 -translate-x-1/2 rounded-lg border border-white/10 bg-zinc-900 p-2 shadow-xl">
+              <div className="absolute left-1/2 top-full mt-2 -translate-x-1/2 rounded-lg border border-white/10 bg-[#0f0f11] p-2 shadow-xl">
                 {secondary.map((p) => (
                   <a
                     key={p.arch}