Make the clock behave on iOS

Two real bugs, both worst on iOS:

The frame was taller than the screen in Safari. .app declared
`height:100dvh;height:100vh`, so the fallback won and 100vh on iOS is the
large viewport — the control bar and part of the bottom panel sat behind
the toolbar. The declarations are now in the right order.

The wake lock never came back. iOS drops it whenever the app backgrounds,
but `lock` was never cleared, so the `!lock` guard blocked every later
re-request and the screen started sleeping mid-game. It now listens for
`release` and clears the handle; against a stubbed API the old code stays
at one request after a release-and-return, the new code makes a second.

Smaller iOS fixes: claim a playback audio session so the ringer switch
doesn't silence the clock (this pauses other audio — the README says how
to drop it), resume the audio context when returning from the background,
suppress the long-press callout, keep sheet scrolling from rubber-banding
the app, back 88dvh with 88vh, and name the home-screen icon.

Untested on real hardware — there's no WebKit engine here, so this is a
code audit plus a Chromium regression run.

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

public_html/sw.js

@@ -1,5 +1,5 @@
 /* Cache-first: once installed the clock never touches the network again. */
-const CACHE = "bgclock-v2";
+const CACHE = "bgclock-v3";
 const FILES = [
   "./",
   "./index.html",