Thin frosted Aero glass, boot-theme fix, latest background revision

The white surfaces were reading as a milky white panel (a card top was
~71% white). The frosted recipes now use a 14% base veil plus the gloss
over the pre-blurred wallpaper, small chrome (rows, chips, segments,
buttons) keeps a touch more veil, and nothing nested inside a sheet or
dialog uses the viewport-aligned layer (it showed the raw dark water
under the settings theme labels at 1.5:1 — nested chrome falls back to
the flat fills over the genuinely blurred sheet).

The first-load text bug was the boot script: its dark test was
`s && !a ? s === 'dark' : matchMedia(...)`, which for a stored aero fell
through to the OS preference, so a dark-preferring machine loaded with
both `dark` and `aero` classes and every `.dark` rule painted over the
wallpaper until a theme toggle re-applied the classes. The stored value
now decides alone; a dark-colorScheme check pins it in the mobile suite
(123 checks).

Background: the user's latest Gemini scene (1280x714) re-encoded to
public/aero/background.webp (206 kB) with a fresh pre-blurred sibling.

Contrast: 0 below-minimum findings, 0 axe violations, all three themes.
Version 0.3.1, SW -> freezmo-v62.

package.json

@@ -1,6 +1,6 @@
 {
   "name": "freezmo",
-  "version": "0.2.9",
+  "version": "0.3.1",
   "private": true,
   "license": "GPL-3.0-only",
   "scripts": {