Major rebranding, i18n, dashboard, shared folders, role capabilities

- Rebrand: new app/agent icons, SKALD.md, warm "paper" CSS palette
  (terracotta accent, --radius tokens, WCAG contrast, reduced-motion),
  updated favicon, tray icon, skaldkonur asset
- i18n: backend crate (i18n.rs, locale column, ui_locale config),
  frontend library (web/lib/i18n.js, I18nMixin, t(key)),
  translation files (web/i18n/), every component wired
- Dashboard: <dashboard-page> replaces old home-page content;
  <app-copilot> becomes the landing page (full/dock layout modes)
- Shared folders: API endpoints (shared_folders.rs), frontend page,
  can_write membership, container mount topology, user_fs routing
- Role capabilities: new db table & authorization seam (data not enums),
  roles.attrs JSON for ui_mode / interface select
- Setup: skald-setup prompts for language + password, sets ui_locale
- General: components migrated to CSS variables, Lit conventions cleanup,
  connectors/catalog/marketplace/approval refactoring

web/components/mobile-app.js

@@ -1,4 +1,5 @@
 import { LitElement, html, nothing } from 'lit';
+import { t }            from '../lib/i18n.js';
 import './shared/inbox-page.js';
 import './shared/chat-page.js';
 import './shared/projects-page.js';
@@ -199,18 +200,18 @@ class MobileApp extends LitElement {
           ${['notifications', 'settings'].includes(s) ? html`
             <div class="mobile-coming-soon">
               <i class="bi bi-tools"></i>
-              <p>Coming soon</p>
+              <p>${t('mobile.coming_soon')}</p>
             </div>
           ` : ''}
         </div>
 
         ${this._native ? nothing : html`
           <nav class="mobile-nav">
-            ${item('inbox',         'bi-inbox',         'Inbox')}
-            ${item('projects',      'bi-folder2-open',  'Projects')}
-            ${item('chat',          '',                 'Chat',    'chat-btn')}
-            ${item('notifications', 'bi-bell',          'Alerts')}
-            ${item('settings',      'bi-sliders',       'Settings')}
+            ${item('inbox',         'bi-inbox',         t('mobile.nav.inbox'))}
+            ${item('projects',      'bi-folder2-open',  t('mobile.nav.projects'))}
+            ${item('chat',          '',                 t('mobile.nav.chat'),    'chat-btn')}
+            ${item('notifications', 'bi-bell',          t('mobile.nav.alerts'))}
+            ${item('settings',      'bi-sliders',       t('mobile.nav.settings'))}
           </nav>
         `}
       </div>