QA Batch: Vendor Downloads, Resolution Center Reliability, Comments Drawer Refactor & Admin Tenant Fixes

This release promotes a batch of frontend fixes and refactors into the QA environment, spanning the Vendor portal, Mail Resolution Center, the Comments drawer, Admin tenant management, and notifications. The headline user-facing wins are reliable file downloads in the Vendor portal, smoother and more resilient Resolution Center forms, and a redesigned Comments experience with proper loading, empty, and error states.

Several rough edges had accumulated on the QA-bound dev branch. Vendor download buttons opened files in a new browser tab instead of saving them (the HTML download attribute is ignored for cross-origin S3/Filestack URLs). Resolution Center forms could be double-submitted or show stale data while saving. The Comments drawer had grown into a single oversized file that was hard to maintain and lacked a clear error/retry path. Admin tenant screens were pointed at a renamed backend route, and enterprise tenants could incorrectly retain a parent.

• Vendor users can now download task and upload-center files directly to disk instead of having them open in a new tab; export buttons show a per-row spinner so it is clear a download is in progress.
• Resolution Center users get forms that lock during save (preventing duplicate submissions) and update instantly via optimistic UI, with cleaner handling of the new tenant_id field.
• Mail users see a Comments drawer with distinct loading skeletons, an empty-state prompt, and an error state with a Retry button instead of silent failures.
• Admins get correct tenant list/create/update behavior, and creating an enterprise/client tenant no longer keeps a parent tenant.
• All users get more reliable unread-notification counts in the dropdown.

Grounded in the diff (~1800 additions / ~1350 deletions across 49 files, batching ~9 commits):

• Vendor downloads: new fetchAndDownloadFile(url, filename) helper in apps/vendor/src/lib/utils.ts that fetches a blob and triggers a save, fixing cross-origin (S3/Filestack) downloads; per-row export spinner in TasksTab.
• Vendor layout/responsiveness: task detail page widened (max-w-4xl -> max-w-7xl) with a sidebar layout; upload modal overflow fixes via min-w-0; richer cloud-upload file list (type icons, tooltips, size formatting) in CloudUploadTab.
• Comments drawer refactor: the monolithic useCommentsDrawer.ts (~721 lines) and CommentsDrawer.tsx were split into focused modules — drawer/list/InfiniteCommentsList, drawer/states/{EmptyCommentsState,CommentsErrorState}, drawer/skeletons/*, and hooks/useCommentsDrawer.{ts,helpers.ts} — adding an explicit error state with retry and hardened payload/error parsing.
• Resolution Center: lock forms during save + optimistic updates (resolution.mutation.ts, mailOverview.store.ts); migrated entity handling to tenant_id across DTOs/types/services; normalized resolution and mail-detail update payloads.
• Admin: tenant routes remapped from /admin/api/entities to /admin/api/tenants; TenantFormDialog now hides the Parent Tenant field and forces parent_id: null for enterprise/client types.
• Notifications: notification-dropdown auto-fetch tuned to find unread items beyond page one while avoiding draining pages after Mark-all-read.
• Config: adds apps/vendor/.env.local pointing the websocket/API env at the dev-api endpoint.

Medium. The Comments drawer was substantially restructured; although behavior is intended to be preserved, regressions in pagination, auto-scroll, optimistic posting, or socket reconciliation are possible. The Admin tenant route rename depends on the matching backend endpoint being live in QA. Note: a committed apps/vendor/.env.local hard-codes dev-api/websocket URLs and localhost app URLs — this should not propagate to higher environments. Mitigation: targeted QA on the touched surfaces and confirming the tenant route exists server-side before promotion.

• Vendor: download files from task detail and upload-center modals — confirm they save to disk (not a new tab) and the export spinner appears per row.
• Vendor: open the upload modal with long filenames and the cloud-upload tab; verify no overflow and that icons/tooltips/sizes render.
• Resolution Center: submit a resolution and confirm the form locks during save, updates optimistically, and persists with the correct tenant.
• Comments: open the drawer and verify loading skeletons, empty state, and error+Retry behavior; post a comment/reply and confirm optimistic send, success, and failure states.
• Admin: list/create/update/delete tenants against /admin/api/tenants; create an enterprise/client tenant and confirm the Parent field is hidden and no parent is saved.
• Notifications: confirm the unread count is accurate across multiple pages and after Mark-all-read.
• Verify the vendor websocket connects against the dev-api endpoint in QA.