fix(web): complete bilingual workspace controls

[Tutitoos]

Plan reference

Phase 8 — Release 1.0 operational web quality follow-up after #184 and #188.

Objective

Make the complete Mailflow web workspace expose consistent English and Spanish visible labels and accessible names across desktop and mobile, and lock the corrected states with browser regression coverage.

Reproduction and evidence

1. Open the authenticated private deployment.
2. Switch the language control to Spanish.
3. Inspect the header, mailbox navigation, label tree, bulk toolbar, row quick actions, account menu, and conversation view.
4. Several accessible names remain English, including Notifications, Account menu, Mailboxes, More actions, and label Expand/Collapse. Some system mailbox labels remain raw uppercase provider roles.
5. Repeat at desktop and mobile widths; current browser coverage does not assert the complete locale/navigation matrix.

No message content or credentials are included.

Scope

• Route remaining web-shell visible labels and accessible names through the translation catalog.
• Present system mailbox labels consistently without altering provider identifiers or user-created labels.
• Preserve account scoping, mailbox actions, hierarchy, responsive layout, and reduced-motion behavior.
• Add browser regression assertions for EN/ES desktop and mobile shell states, menus, labels, and conversation controls.

Tasks

• Inventory untranslated web-shell strings and raw system mailbox labels
• Add complete EN/ES catalog entries
• Wire header, navigation, toolbar, account, label tree, row, and conversation controls to translated names
• Add browser regression coverage for both locales and representative viewports
• Validate unit, type, build, translation, and browser suites
• Verify the authenticated deployment with the Codex integrated browser

Acceptance criteria

• Spanish mode exposes no known English shell/action accessible names.
• English mode remains unchanged and coherent.
• Drafts, Sent, Spam, Trash, Inbox, and All mail use translated display labels while provider/user labels remain intact.
• Label expand/collapse names are localized and preserve hierarchy behavior.
• Desktop and mobile render without document overflow.
• Browser tests cover the language menu, expanded/collapsed sidebar, More mailboxes, label hierarchy, row actions, account menu, and conversation controls.
• No new console errors or reduced-motion regressions.

Validation

• bun run --cwd apps/web test
• bun run --cwd apps/web typecheck
• bun run --cwd apps/web build
• go test ./internal/modules/translations
• bun run --cwd apps/web test:e2e
• Authenticated desktop and mobile review in the Codex integrated browser

Dependencies

None. Builds on merged PRs #185, #187, and #189.

Risks

Translation-key drift can make controls unnamed or break locale switching. System mailbox display mapping must not change provider role semantics. Browser tests must avoid mutating real mail.

Out of scope

Bundle/code-splitting optimization, Tauri module loading, new mailbox capabilities, provider data changes, sending mail, and destructive actions.