Rename to 404 Layers, and give it a real icon

The name was SP-404MK2 layers, which is 16 characters and truncates in
the launcher. It is set in five places, one of which cap sync
regenerates from appName, so all five move together: capacitor.config,
strings.xml, index.html, package.json and CLAUDE.md. reference/ keeps
the old name because it is frozen. appId is untouched - changing it
would make this a different app to Android, meaning a fresh install and
the drill progress on the phone orphaned.

The icon is a 3x3 pad grid with the centre pad lit: the app's own
subject, legible when a launcher masks it to a circle, and in the
settled palette. Three columns rather than the hardware's four so the
cells survive 48px, which I checked at 800% magnification.

scripts/make-icon.mjs draws it with ImageMagick primitives, because
there is no SVG rasteriser here - no Inkscape, no rsvg-convert, and no
SVG delegate in ImageMagick 6. It is in the repo because the icon would
otherwise be 15 binary PNGs with no record of how they were made.

Two things that took a few attempts. The draw commands have to be built
as a real array: three tries in bash collapsed all nine into one
argument, which ImageMagick read as a filename. And the convert calls
need -strip, because without it the pixels are identical between runs
but the bytes are not, so the PNGs churned and the script could not be
shown to be their source. Two consecutive runs are now byte-identical.

Also removed two orphaned Capacitor vectors, 204 lines of gradient
swoosh and grid pattern that nothing referenced once the adaptive icon
pointed at @mipmap and @color.

Icons total 52KB. Built and installed.

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

capacitor.config.json

@@ -1,6 +1,6 @@
 {
   "appId": "dev.ncode.sp404layers",
-  "appName": "SP-404MK2 layers",
+  "appName": "404 Layers",
   "webDir": "dist",
   "android": {
     "backgroundColor": "#151719",