feat(web): switch to the Alpine CSP build; drop 'unsafe-eval' from CSP

Standard Alpine evaluates every attribute expression through
new Function(), which a strict Content-Security-Policy cannot allow.
Swap to the official CSP-safe build (@alpinejs/csp), whose parser
evaluates expressions against registered component scope without
eval. script-src now carries only 'self' and 'unsafe-inline' (the
latter still required by the pre-paint theme flash guard).

Bindings rewritten out of the unsupported expression shapes:
- 21 multi-statement sequences across admin, audio_reader, docs,
  header, index, and reader became single component methods
  (init/loadWatchStatus hooks, commitScrub, pickSkip, pickSpeed,
  pickDefaultSpeed, chooseSleepOption, chooseSleepClockMode,
  toggleFxInvert, openPageThumbs, submitNote, clearSearch,
  pickReadingTheme)
- the header sidebar's inline x-data (openPanel/themeMode IIFE)
  became a registered sidebarShell component; openPanel itself moved
  to the header root so every sidebar panel shares one open state
- the appearance-panel  moved into the component init()
- header init() now also seeds openPanel from localStorage (or the
  admin section on /admin pages)

Alpine magics (, , , ) remain available —
the CSP evaluator injects them into scope.

The Playwright suite covers the converted surfaces end to end.

web/src/alpine.ts

@@ -1,4 +1,4 @@
-import Alpine from "alpinejs";
+import Alpine from "@alpinejs/csp";
 
 // Extend Window interface to include Alpine. The `htmx` member is declared
 // once in shims.d.ts — redeclaring it here with a different shape is a