feat(about): rebuild the About box as a conversion surface

Creator: the About box was "shitty" — an unreadable logo, a version number nobody asked for, copy that
insulted the creator, and buttons that looked like text. Rebuilt around one job: convert.

- **820×860 modal** (was 650×700) with a scrollable hub, and the logo at **520 px wide** instead of
  125 — the asset is 2816×1536, so it was being drawn as a thumbnail, not an icon problem.
- **Pre-Release pill** replaces "Version 1.0.0" (the assembly version stays in log lines). The pill is a
  button: it opens llamacasty.com until a Steam store page exists, so the link changes in one place.
- Tagline: "1-2-3, and go live to the world on YouTube!" The old "simple enough that even the most
  right-brained person can intuit it" is gone, and a test asserts it stays gone.
- The offer in three short blocks (free 30 fps · paid 60 fps · one-time, lifetime, no account /
  subscription / tracking), then the launch price and **one primary CTA**: "Unlock 60 fps — $79".
- Price: $79 until **April 1, 2027**, then $99 locked for life. The numbers live once, in
  `MainViewModel.Overlays`, and are recorded in `docs/ai/commercial.md`.
- **A paying customer is never sold to**: ownership collapses the price/CTA block and shows
  "Licence: owned via Steam — thank you."
- Secondary destinations (channel, Mastodon, coffee, licences) are one quiet row; footer is
  `© Llama Chile Shop`; the "Made by gramps" line is removed.
- `YtButtonSecondary` now carries a higher surface, a hairline border and a keyboard focus ring — they
  were the same tone as the panel behind them, which is why they read as plain text.

Test: `AboutHubTests.About_ShowsTheOfferToFreeUsers_AndNothingToSellToOwners` — tagline, pill, price,
CTA text, copyright, the removed lines stay removed, and the CTA block collapses when owned.
FAST gate: 540 passed, 0 failed, 0 warnings.

ViewModels/MainViewModel.OutputProfile.cs

@@ -25,6 +25,7 @@ public partial class MainViewModel
             EntitlementErrorMessage = _entitlement.ErrorMessage;
             if (!changed) return;
             OnPropertyChanged(nameof(HasProOutput));
+            OnPropertyChanged(nameof(LicenceStateLabel));
             RefreshSteamLicenceAlert();
             if (!HasProOutput && _selectedQuality is { RequiresPro: true } && CanChangeQuality)
                 SelectedQuality = QualityOptions.Single(option => option.Display == OutputProfile.FreeFallbackName);
@@ -78,6 +79,7 @@ public partial class MainViewModel
             if (!DevBuild.IsDevelopment) return;
             if (!SetProperty(ref _developerMode, value)) return;
             OnPropertyChanged(nameof(HasProOutput));
+            OnPropertyChanged(nameof(LicenceStateLabel));
             RefreshSteamLicenceAlert();
         }
     }