feat(ui): app icons on the house canvas; detail page gets the tile treatment

- alby-hub + phoenixd icons re-set with the standard 12% inner margin
  (they shipped edge-to-edge; every other icon carries whitespace).
- scripts/normalize-app-icon.py: wraps any third-party SVG mark onto the
  house canvas — the system applies the tile plate (archy-app-icon)
  automatically but deliberately no runtime inset, so the margin must be
  baked; the guide now says exactly that.
- MarketplaceAppDetails: the icon now carries archy-app-icon like the
  store tiles — the treatment no longer stops at the detail page.
- v1.8.2 changelog: third curated bullet (the ceremony gate requires 3).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

CHANGELOG.md

@@ -3,7 +3,8 @@
 ## v1.8.2-alpha (2026-08-13)
 
 - **An app that can't be shown inside the dashboard now becomes a tab app by itself.** A few apps refuse to render inside another page no matter what — they break out with their own code or insist on owning the whole browser window. Opening one used to mean staring at a grey pane. Now the dashboard notices, offers the app in its own tab, and remembers: from then on that app's button opens a tab directly (with the little launch icon that tab apps carry), first click, every time. If a later update makes the app embeddable after all, the dashboard notices that too and goes back to embedding it.
-- **The screensaver and login emblem are back to their clean black finish.** A glossy paint experiment on the circle behind the logo shipped by mistake in the previous update; it's removed everywhere.
+- **The logo emblem got its glossy black paint finish — properly this time.** The circle behind the A on the screensaver, intro, and login now wears a deep wet-paint look: warm light blooming from the top edge, fine grain so the dark tones stay smooth instead of banding, and no more ring border. (An earlier rougher version of this experiment briefly shipped by accident and then vanished depending on which screen you were on — this is the finished, deliberate one, everywhere.)
+- **New app icons now match the store's look, on every screen.** Alby Hub and phoenixd arrived with edge-to-edge logos that ignored the breathing room every other app icon has, and the app detail page skipped the icon backdrop entirely. Both icons are re-set on the standard canvas, the detail page now applies the same icon treatment as the store tiles, and app developers get a one-command tool that puts any logo onto the house canvas automatically.
 
 ## v1.8.1-alpha (2026-08-13)