Mail & Document Fixes: PDF Zoom, Bulk Delete, Assignment Flow, and Caching (QA)

A QA batch bundling five frontend fixes across the Mail and Document experiences: consistent PDF preview zoom, a new "delete all documents" action in mail details, a smoother move-to-processing assignment flow, suppression of browser autofill on share-mail address fields, and reduced redundant network calls by caching entity types. These are targeted bug fixes and refinements, not new modules.

QA and production usage surfaced several rough edges: PDFs previewed inside the iframe opened at an inconsistent zoom; users had no quick way to clear all documents on a mail; the client blocked moving mail to "Processing" with its own assignment check that could diverge from backend rules; password managers overlapped the To/Cc/Bcc fields in the share-mail dialog; and entity-type lookups re-fired on every page that opened a resolution modal.

• PDF previews now open at page width with horizontal fit, so documents render at a predictable size every time.
• Users with delete permission get a one-click "Delete all documents" button (with a confirmation prompt) in a mail's Documents view.
• Moving mail to Processing no longer trips client-side blocks; the backend is the single source of truth for assignment rules, giving consistent error messages.
• The share-via-mail recipient fields no longer collide with password-manager popups.
• Resolution assignment screens load faster and make fewer duplicate calls because entity types are cached once.

Bundles feature PRs #698, #699, #700 plus follow-ups:

• PDF zoom (#698) PDFViewerCore.tsx: appends zoom=page-width and view=FitH hash directives (guarding against duplicates) and resolves relative file URLs against window.location.href.
• Bulk delete MailDocuments.tsx: adds permission-gated "Delete all documents" button + ConfirmationPrompt, optimistic state pruning, and cache invalidation; deletes via new mail_ids payload.
• Assignment flow (#700) MailContents.tsx, columns.tsx: removes client-side "assign before Processing" guards from row, drawer, and single-transition paths; defers validation to the API.
• Autofill (#699) ShareViaMailDialog.tsx: per-field ids/names and data-lpignore for To/Cc/Bcc.
• Entity-type caching new constants/queryKeys.ts (ENTITY_TYPES_QUERY_KEY); useGetEntityTypes consolidated into entityType.queries.ts with enabled toggle; duplicate getEntityTypes service/route removed; lists memoized in two resolution modals.
• Service document.services.ts: deleteDocument now accepts mutually-exclusive document_ids/mail_ids, makes updated_by optional, and validates that an identifier is present.
• Minor: responsive layout for mail-details tabs and document header; AGENTS.md doc-rule wording.

Moderate, well-scoped. The main behavior change is removing client-side assignment validation for move-to-processing, so the backend must reliably reject unassigned transitions and return clear messages; otherwise users could be allowed to start a transition that then fails. "Delete all documents" is destructive but gated by permission and a confirmation prompt. The PDF URL handling adds parsing branches (relative URLs, malformed hashes) that fall back to the raw URL on error. Mitigation: this is a QA-stage batch intended for testing before production promotion.

• Preview multiple PDFs (cloud-stored and relative paths, with/without existing hash params) and confirm they open at page width without double zoom directives.
• As a user with delete permission, use "Delete all documents" on a mail; confirm the prompt, removal, and that grids/counts refresh; verify the button is hidden without permission or when there are no documents.
• Move mail to Processing from row menu, drawer, and single-transition button while unassigned and assigned; confirm backend errors surface correctly and the assign-user retry flow still works.
• Open the share-via-mail dialog and confirm To/Cc/Bcc fields do not trigger password-manager overlays.
• Open resolution Add/Assign modals across several pages and confirm entity types load from cache (no repeated network calls) and selectors populate.