Aero: heavier shared blur, and the composer field reads as a field

The composer's input was still a flat 60% white bar (the "clean, even tile"
from the earlier pass) on a panel that had rightly become translucent, so it
read as a white slab - "especially the part where you enter the prompt". It is
now the app's standard frosted tile plus one light veil: measured against the
same backdrop the field sits at 178,212,157 where the panel is 145,183,79 -
clearly a brighter field, still glass.

Translucent glass needs softness rather than opacity, so the shared backdrop
(background-blur.webp, the pre-blurred copy every Aero surface sits on) is
re-baked much softer - a 64x36 upscale - and every panel, card, chip and
button now shows the scene as an even frosted wash instead of white or mud.
?v=5 busts the asset.

Contrast scans stay clean (chat, library, study, settings across all three
themes, 0 findings) and all 15 suites pass. Version 0.6.4, SW v86.

public/sw.js

@@ -9,7 +9,7 @@
  *
  * Bumping CACHE_VERSION is how a new deploy invalidates old assets.
  */
-const CACHE_VERSION = "freezmo-v85";
+const CACHE_VERSION = "freezmo-v86";
 const SHELL_CACHE = `${CACHE_VERSION}-shell`;
 const ASSET_CACHE = `${CACHE_VERSION}-assets`;