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/static/js/metrics.js

@@ -18,8 +18,8 @@ function rangeQS() {
 }
 
 function card(label, value, hint) {
-  return `<div class="card"><p class="muted" style="margin:0">${esc(label)}</p>
-    <p style="font-size:1.6rem;font-weight:700;margin:4px 0">${esc(value)}</p>
+  return `<div class="card stat"><p class="stat-label">${esc(label)}</p>
+    <p class="stat-value">${esc(value)}</p>
     ${hint ? `<p class="hint">${esc(hint)}</p>` : ''}</div>`;
 }