Add a ?pi=1 profile, and stop re-deriving search keys per keystroke

Two separate costs, both measured on musicdolphin (Pi 4, 1920x1080 kiosk), where the
app was burning ~70% of a core with nothing happening on screen.

Per-frame work. The ambient canvas repaints a full-screen gradient plus a particle
field every frame, and `usePlaybackClock` pushes a React setState per animation frame
into both PlayView and PlayerBar for the whole length of a track. `?pi=1` (lib/
lowPower.ts) makes those cheaper rather than switching them off: the canvas paints a
quarter of the pixels at 30fps with a bubble cap, and the clock renders ten times a
second - a progress bar advances one pixel every few hundred ms and its label has
one-second resolution, so nothing on screen can tell. Only the effects with no cheap
version actually go: the backdrop-filter glass blur and the decorative CSS loops.
Also drops a redundant full-canvas clearRect that the opaque gradient always covered.

Search. normalize() runs a Unicode NFD decomposition, and albumMatches/songMatches
called it on every album title and every track title on every keystroke - 4969 of them
for a track search, whose answer cannot change until the library does. buildSearchIndex
does it once per library payload; a keystroke is now String.includes over strings that
already exist. On the real library that is 33ms -> 3.4ms for an eight-letter track
query on a laptop, and this runs on a Pi. The same index partitions albums by shelf and
pre-sorts each shelf's categories, which App and BrowseView were deriving separately
from the same data.

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

web/src/lib/tippen/theme.ts

@@ -4,17 +4,24 @@
  * through components. The hue lives in styles/app.css because CSS is where it is used;
  * it is repeated here only for the canvas, which cannot read a custom property. */
 
+import { LOW_POWER } from "../lowPower";
+
 /** The turquoise lagoon. Music is 210, Hörbücher 55, "Mein Zimmer" 300. */
 export const HUE = 175;
 
-/** Frost the glass panels with a real backdrop blur. Expensive on weak GPUs. */
-export const SHOW_GLASS_BLUR = true;
+/** Frost the glass panels with a real backdrop blur. Expensive on weak GPUs, and the
+ * on-screen keyboard frosts every single key - off under `?pi=1`, like the music app's
+ * matching toggle. */
+export const SHOW_GLASS_BLUR = !LOW_POWER;
 
-/** The decorative rising bubbles behind everything. */
-export const SHOW_BUBBLES = true;
+/** The decorative rising bubbles behind everything. A dozen elements animating forever,
+ * carrying no information, so `?pi=1` drops them. */
+export const SHOW_BUBBLES = !LOW_POWER;
 
 /** The earned pets swimming behind every screen. The reward that is always in view - off
- * only to rule it out when chasing a performance problem. */
+ * only to rule it out when chasing a performance problem. Kept on even under `?pi=1`: a
+ * handful of images moved by writing `transform`, and taking away what she earned to save
+ * a few frames is the wrong trade. */
 export const SHOW_AQUARIUM_CREATURES = true;
 
 /** Fade screens in on entry. */