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

crates/skald-core/src/db/mod.rs

@@ -400,6 +400,7 @@ async fn create_registry_tables(pool: &SqlitePool) -> Result<()> {
             database_password BLOB,
             password_hash     BLOB,
             active            INTEGER NOT NULL DEFAULT 1,
+            locale            TEXT,
             created_at        TEXT    NOT NULL DEFAULT (datetime('now')),
             updated_at        TEXT    NOT NULL DEFAULT (datetime('now')),
             CHECK (
@@ -410,6 +411,8 @@ async fn create_registry_tables(pool: &SqlitePool) -> Result<()> {
     )
     .execute(pool)
     .await?;
+    // Per-user UI locale override is additive — reaches an existing DB in place.
+    ensure_column(pool, "users", "locale", "TEXT").await?;
 
     // Shared on-disk folders (blueprint §6/§0.1): a named directory
     // `{WD}/shared/{folder_name}` bind-mounted into the container of each member.
@@ -422,11 +425,16 @@ async fn create_registry_tables(pool: &SqlitePool) -> Result<()> {
         "CREATE TABLE IF NOT EXISTS shared_folders (
             id          INTEGER PRIMARY KEY AUTOINCREMENT,
             folder_name TEXT    NOT NULL UNIQUE,
+            description TEXT    NOT NULL DEFAULT '',
             created_at  TEXT    NOT NULL DEFAULT (datetime('now'))
         )",
     )
     .execute(pool)
     .await?;
+    // The folder's description is injected into the agent's system context so it
+    // knows what each shared folder holds and when to read/write it. Additive —
+    // reaches an existing DB in place (a no-op on the fresh CREATE above).
+    ensure_column(pool, "shared_folders", "description", "TEXT NOT NULL DEFAULT ''").await?;
 
     sqlx::query(
         "CREATE TABLE IF NOT EXISTS shared_folder_members (