feat: add translation foundation

[mardausdennis]

Summary

• add an authenticated GET-only endpoint for the current user's Frappe translations
• load translations before Builder's initial router navigation, with English error and timeout fallback
• localize representative Builder strings and register TypeScript extraction

Validation

• 11 translation helper tests
• 6 Frappe integration tests, including endpoint authorization and canonical catalog locations
• Linux production build with Node 24 and Vite 5.4
• 3 Cypress startup/error/timeout scenarios on a disposable Frappe site

[greptile-apps]

Confidence Score: 5/5

The PR appears safe to merge.

No blocking failure remains.

_{Reviews (3): Last reviewed commit: "Merge upstream develop into feat/builder..." | Re-trigger Greptile}

[mardausdennis]

@surajshetty3416 The implementation and follow-up review fix are ready. Greptile is 5/5 and the addressed thread is resolved. Linters, UI Test, and Server Tests are currently action_required with 0 jobs executed, so they still need maintainer approval to run. Could you approve the workflows and review the PR when convenient?

[mardausdennis]

Updated the branch with a normal merge of current develop (�093eab6). The PR is now conflict-free and GitHub reports it as mergeable. Fresh validation against this exact merge head passed: translation helper 12/12, production build (2,611 modules), full Builder server suite 86/86 including real POT extraction, and Cypress i18n 3/3 in Chrome with retries disabled. Greptile has also re-reviewed the new head at 5/5. The new Linters, Server Tests, and UI Test runs are still �ction_required and need maintainer approval: 30861276815, 30861276820, 30861276856. @surajshetty3416 could you approve those workflows and review when convenient?