feat: Y2K dither theme, filter toolbars, chat bubble widget; fix alignment root causes

- theme rework (user request): white paper bg, brown ink, ordered-dither
  halftone textures, hard offset Y2K shadows, dithered masthead bands;
  dark theme matched; token test + DECISIONS updated
- fix: .card + .card stacking margin leaked into grid layouts, shifting
  every card except the first (the 'always the first item' reports)
- fix: CSP style-src 'self' silently dropped every inline style attribute
  (misaligned save button, stat values, editor attach button, bell badge);
  styles now allow inline, scripts remain strict per §12
- fix: [hidden] is now display:none !important so flex containers cannot
  defeat it (chat panel/footers)
- board + metrics filters live in boxed .toolbar rows with baseline-aligned
  controls; metric stat cards use a uniform .stat layout
- new-conversation dialog: fixed 440px width and 180px results list (no
  more resizing while searching), full-width result rows, picked people
  drop out of the list
- floating messages bubble bottom-right on all pages (except /messages):
  unread badge, mini panel with conversation list, thread view, quick
  composer, live WS updates; toasts moved up to clear it

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

web/templates/layout.html

@@ -58,7 +58,8 @@
   <div id="toasts" aria-live="polite"></div>
   <script type="module" src="/static/js/nav.js"></script>
   {{if .User}}<script type="module" src="/static/js/notifications.js"></script>
-  <script type="module" src="/static/js/shortcuts.js"></script>{{end}}
+  <script type="module" src="/static/js/shortcuts.js"></script>
+  <script type="module" src="/static/js/chat-widget.js"></script>{{end}}
   {{range .Scripts}}<script type="module" src="{{.}}"></script>
   {{end}}
 </body>