relay UI overhaul, favicon, settings, admin last-seen, fixes

Relay:
  - Inbox/shared/sent split into own view-inbox (nav button + poll).
    Compose is now single-column, centered.
  - Header logo links to compose. Inbox badge stays fresh on all
    views via a quiet loadInbox on every view switch.
  - Mobile menu: full-height sheet below header, larger buttons
    (15px font, 14px padding), full width.
  - Login form wrapped in <form> with name attributes + for/id on
    labels so password managers can autofill.
  - Admin user list shows "last seen <relative time>" per user.
    last_seen_at column on tenants, updated on every authenticated
    request (session + client API).
  - Cache-busting on style.css + app.js via filemtime.
  - View persistence in localStorage (survives reload).
  - Shared-bucket cards show title only (preview line removed).

Favicon:
  - favicon.svg added to project root + copied to public/, relay/,
    website/. Linked via <link rel="icon" type="image/svg+xml"> in
    all three <head> sections.

Settings:
  - New toggle: "Show shopping list items in task collector"
    (default off). collectTasks skips #einkauf/#shopping cards when
    disabled.

Fixes:
  - card-spinner gets display:inline-block so it rotates outside
    flex containers (shopping save spinner).
  - Tim tab test opens the plugin before checking active state.
  - Compose view centered with margin:auto on desktop.

Bumps to 1.9.29.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

public/css/style.css

@@ -395,6 +395,7 @@ body.settings-peeking #settings-overlay > div { pointer-events: auto; }
 .settings-tab.active { color: var(--t-accent); border-left-color: var(--t-accent); background: color-mix(in srgb, var(--t-accent) 8%, transparent); }
 
 @keyframes spin { to { transform: rotate(360deg); } }
+
 @keyframes pulse-glow { 0%, 100% { opacity: 1; } 50% { opacity: 0.35; } }
 .card-bar-pulse { animation: pulse-glow 2s ease-in-out infinite; }
 .board-card:has(.card-bar-pulse) { border-color: var(--t-danger); }
@@ -402,7 +403,7 @@ body.settings-peeking #settings-overlay > div { pointer-events: auto; }
 .card-done-badge { position: absolute; bottom: 0; right: 0; width: 0; height: 0; border-style: solid; border-width: 0 0 24px 24px; border-color: transparent transparent #4ade80 transparent; z-index: 1; }
 .card-done-badge i { position: absolute; bottom: -22px; right: 1px; font-size: 10px; color: #000; }
 .board-card:has(.card-bar-pulse) .card-bar-pulse ~ * .text-t-danger { animation: pulse-glow 2s ease-in-out infinite; }
-.card-spinner { animation: spin 0.8s linear infinite; }
+.card-spinner { animation: spin 0.8s linear infinite; display: inline-block; }
 
 /* Cards */
 .card-bar { image-rendering: pixelated; height: var(--ui-bar-height, 3px); }