Pi profile: no glass blur, keep the drift; consolidate the perf knobs

With the ambient canvas off under ?pi=1, the backdrop blur no longer buys anything:
it paid for itself by giving each panel a compositing layer above the animating
canvas, and with nothing animating underneath it was just cost - enough to make the
browse rows visibly sluggish on the device. So the Pi profile now drops every backdrop
blur (`glassBlur`, which the music app and the typing game share), and turns the
drift and the moving mascot back on: plain CSS transform loops the compositor runs by
itself, which measured as noise.

The knob set is consolidated to match: one glass toggle instead of panel and card
blur, one shadows toggle for cards and tiles, the typing game's drift and view
transitions folded into the shared ones, and the backing-store cap fixed by profile
rather than a setting. The parent dialog groups them into Darstellung / Abspielen /
System and hides the canvas tuning while the canvas is off. Stored settings move to
musicmouse.perf.v2, since v1 drafts held the old preset in full.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

web/src/components/BrowseView.tsx

@@ -766,7 +766,7 @@ export function CategoryTile({
           : `oklch(95% 0.015 ${GROUP_HUE.music} / .66)`,
         borderRadius: allBooks ? "6px 18px 18px 6px" : "16px",
         // One blurred shadow per tile: dropped under `?pi=1`, like `cardShadow`.
-        boxShadow: PERF.tileShadows ? "0 6px 18px var(--shadow)" : "none",
+        boxShadow: PERF.shadows ? "0 6px 18px var(--shadow)" : "none",
       }}
     >
       <div