Extract CSS/JS to static files, wrap header pills, add version footer

The palette lived in a :root block duplicated across all three
templates, so every reshade meant three edits — and drifted twice in
practice (the favicon hardcoded its own hex; stale danger-border rgba
literals survived two palette changes). Move tokens to a single
static/css/base.css, derive every dim/border tint from the four source
hues with color-mix, and point the favicon at one static/favicon.svg.

Also splits the 1558-line dashboard.html into template + static assets:
662 lines of CSS and 396 of JS were re-sent uninlined on every load
with no browser caching, which costs real time on the remote/cellular
access this app is built for. Templates drop to 501/42/107 lines.
Server-rendered config (timezone, script_root) now arrives via
<body data-*>; wiring URL_BASE to request.script_root also fixes /api/*
fetches for a future subpath mount, which the hardcoded "" would break.

Header service pills now wrap instead of scrolling — they were clipped
at narrow widths, and a hidden pill is a service whose status you
cannot see. Verified 0 clipped and no page overflow at 320/375/700/1280.

Footer gains a version and date so the running build is identifiable
without trusting the Unraid Docker tab's cached container IDs.

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

static/favicon.svg

@@ -0,0 +1,4 @@
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 100 100">
+  <rect width="100" height="100" rx="22" fill="#7c86ff"/>
+  <path d="M40 32 L72 50 L40 68 Z" fill="#141416"/>
+</svg>