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/agent-inbox.js

@@ -1,8 +1,9 @@
 import { html, nothing } from 'lit';
 import { LightElement }  from '../lib/base.js';
 import { InboxMixin }    from '../lib/inbox-mixin.js';
+import { t, I18nMixin }  from '../lib/i18n.js';
 
-export class AgentInboxPage extends InboxMixin(LightElement) {
+export class AgentInboxPage extends I18nMixin(InboxMixin(LightElement)) {
 
   static get properties() {
     return {
@@ -58,7 +59,7 @@ export class AgentInboxPage extends InboxMixin(LightElement) {
       <div class="page-panel">
         <div class="page-panel-header">
           <h5 class="mb-0">
-            Agent Inbox
+            ${t('nav.inbox')}
             ${total > 0 ? html`<span class="badge bg-danger ms-2">${total}</span>` : nothing}
           </h5>
           <button class="inbox-refresh-btn" title="Refresh" @click=${() => this._loadInbox()}>