2026-04-19 — Offline-first writes + entity outbox

Commits b92f1ef, adcddd7.

What

• Implemented offline-first writes for transactions backed by an IndexedDB outbox (src/lib/offline/outbox.ts, sync.ts).
• Extended outbox coverage to banks, categories, and wishlist via per-entity merge logic (mergeBanksOutbox.ts, mergeCategoriesOutbox.ts, mergeWishlistOutbox.ts).
• Added OutboxSyncContext, useOutboxSync, usePendingEntities, usePendingTransactions hooks for UI awareness of pending state.
• PWA service-worker tuning for performance.

Why

Adding a transaction on mobile while offline (commute, no signal) was the dominant unmet use case. Without an outbox, the form just failed silently. The outbox makes the PWA actually useful as a "capture now, sync later" tool. Extending to all mutable entities meant onboarding (creating a first bank/category) also works offline.

Touches

• src/lib/offline/ (new module)
• src/app/(main)/* — UI for pending indicators
• next.config.* — PWA tuning
• tests/e2e/offline-*.spec.ts — E2E coverage

Gotchas

• Server-side merge must be idempotent; outbox can replay the same write. See [[Projects/personal-finance-notion/runbooks/runbook-pwa-outbox-stuck|runbook-pwa-outbox-stuck]].
• New entity types must register dispatchers in entity-dispatch.ts and merge logic — easy to miss when adding a model.