Mail & Admin Frontend Batch: Live Bulk-Action Progress, Failure Details, and Loading Polish (QA)

A batch of seven frontend fixes was promoted from dev to the QA environment. It makes bulk mail actions report progress over the live notifications connection (with a reliable fallback), surfaces exactly which items failed in a partial bulk operation, stabilizes loading skeletons and PDF thumbnail rendering, and tightens several mail/admin UI details. No new end-user feature is introduced beyond these improvements; this is a quality and reliability pass now entering QA testing.

Bulk mail operations (bulk assign, bulk update) previously leaned on immediate HTTP polling and could show jumpy or incomplete progress, and a partially failed bulk action gave no indication of which items failed. Separately, the frontend's real-time WebSocket types had drifted from the backend's actual message contracts, the socket could churn (disconnect/reconnect) when navigating between sections, table/grid loading states caused layout jumps, and a few smaller issues (missing tenant labels on users, mis-handled deleted-user references, dropdowns unscrollable inside dialogs) degraded the experience.

• Bulk mail actions now prefer the live notifications connection for progress, with a graceful HTTP fallback only when the socket is slow or quiet, giving smoother and more accurate progress.
• When some items in a bulk action fail, the bottom-right progress panel now shows a clear summary (e.g. "X/Y updated, Z failed") plus an expandable list of the specific failures.
• Loading states for admin tables and mail grids no longer jump around, and PDF thumbnails render more reliably.
• Users now show their tenant badge when assigning to folders; deleted users display consistently as "Deleted User"; large user-pick lists load page-by-page as you scroll; and dropdowns inside dialogs scroll correctly.

Promotion of origin/dev into qa; no code added on top of dev. Notable included PRs:

• #954 socket-first bulk progress: BulkOperationProgress now enables HTTP polling only after grace windows (connect 2s, first-event 10s, stale 5s); adds successful/failed counts and failedDetails, a new BulkOperationProgressFailureDetails panel, and a guarded single-fire completion path.
• #952 loading stabilization: new data-table-skeleton-row / data-grid-skeleton-row with shimmer + staggered fade; tables lock cached column widths during load; PdfThumbnailGrid render-safety fixes.
• #950 WS contract alignment: rewrites packages/types/websocket.types.ts and the comments/upload/download/job socket hooks to match backend envelopes; adds close-code 1013 to skip-reconnect.
• #948 socket lifecycle: hoists NotificationsSocketProvider to the mail root layout via a new AuthenticatedSocketProvider, adds bfcache pagehide/pageshow handling and telemetry.
• #949 tenant badges + paginated multi-select: AdminMultiSelect gains onPaginatedSearch infinite scroll (cached, 20/page); UserMultiSelect adopts it; folder modals map entity_name.
• #947 deleted-user sentinel: new user.constants.ts; activity logs/comments map sentinel deleted_user to "Deleted User" and keep "System" for null.
• #946 review-bug fixes: numeric-id guard in user modals, infinite-retry break in MailForm label resolver, async-select label priority.
• #950/#949 popover-in-dialog: combobox/multi-select portal into the dialog container.

Moderate, touching real-time progress and shared UI primitives. The socket-first progress path is timing-dependent: if the grace windows are mis-tuned, progress could stall before HTTP fallback kicks in, or briefly double-poll. WebSocket type changes are broad and could surface mismatches if backend contracts differ from the documented ones in QA. Mitigations: HTTP polling fallback still guarantees terminal completion; completion is single-fire guarded against duplicate signals; changes are additive UI improvements with existing flows preserved; QA is the intended gate before production.

• Run bulk mail update/assign over a large selection: confirm live progress updates, accurate percentage, and timely terminal state with the socket connected and (force) when it is not.
• Trigger a bulk action with some items failing: verify the "X/Y updated, Z failed" summary and the expandable failure-details list show correct items.
• Navigate between dashboard and batches mid-operation: progress should persist without socket reconnect churn; check bfcache (back/forward) behavior.
• Verify admin tables and mail grids show stable skeletons (no layout jump) and that PDF thumbnails render without flicker/errors.
• Confirm tenant badges on users in folder assign modals, "Deleted User" display in activity logs/comments, infinite-scroll user lists, and that combobox/multi-select dropdowns scroll inside dialogs.