fix(transactions): persist the source filter per company and stop the reset race (#1726)

The source filter was persisted under a browser-wide v1 key (#1105), but
the stale-filter guard added in #1124 compared the restored value against
sourceItems before cash accounts, skattekonto rows, and transactions had
loaded, so every mount reset the in-memory filter back to 'Alla källor'
while storage kept the old choice: restore-then-reset on every visit.

- New pure helper components/transactions/source-filter-storage.ts:
  per-company v2 key, isSourceFilter moved out of the page, read/write
  helpers (read removes the retired v1 key once), and
  resolveEffectiveSourceFilter.
- page.tsx keeps sourceFilter as the WANTED filter, restored per company
  (with a state-only ?source= URL override that is never written to
  storage); the guard effect is replaced by a derived
  effectiveSourceFilter memo used by every consumer, so a source that is
  still loading or went stale shows 'all' without destroying the choice.
- ?highlight= deep links widen to 'all' in memory when the wanted filter
  would hide the highlighted row.
- Unit tests for the helper; no i18n changes, no migrations.

Co-authored-by: Jakob Wennberg <311770904+jakobwennberg-oss@users.noreply.github.com>
Co-authored-by: Claude Fable 5 <noreply@anthropic.com>

DECISIONS.md

@@ -1092,3 +1092,4 @@ One line per decision: `[YYYY-MM-DD] <decision>: <why>`. Appended by agents and
 [2026-08-19] Hem build-assistant hero downgraded to the quiet-sentence pattern (AgentPromo, matches SkatteverketPromoCard; founder direction 2026-08-18 'redesign first, maybe remove later'): dismissal is per-company localStorage (erp_agent_promo_dismissed:<companyId>) like the SKV promo, gate and hasAi/billing routing unchanged.
 [2026-08-19] Banking settings UI state derives from a pure helper (extensions/general/enable-banking/lib/connection-state.ts), not inline JSX conditions: sort precedence, the single page-level .attn sentence, and each row's one primary action must agree on which state a connection is in, and only a pure module can unit-test that. The same-bank connect intercept excludes 'pending' rows (an in-flight authorization is not a renewable connection) and the fresh-connect body sends force_new: true after the intercept so the parallel 409 server guard can distinguish deliberate second connections; 'pending' rows now render as a spinner row ("Väntar på banken") for their whole lifetime instead of only locking the connect button for 30 s, since an invisible in-flight row was the confusion.
 [2026-08-19] Bank reconnect supersede reuses status 'revoked' plus a new superseded_by column instead of a new status value, and re-points transactions.bank_connection_id to the superseding row: every existing filter, ledger-claim release, and cron skip already handles 'revoked' correctly (no CHECK-constraint migration on a live table), superseded_by disambiguates a supersede from a user disconnect, and re-pointing the feed rows (plain FK metadata, never journal tables) is what makes the picker's gap-fill probe and per-connection scoping survive a renewal.
+[2026-08-19] /transactions source filter persists in per-company localStorage (v2 key) rather than user_preferences.ui_state, matching the FyPicker/JournalEntryList page-scoped filter idiom (design rule 9 reserves ui_state for split-button modes/nav), and a derived effectiveSourceFilter memo replaces the stale-filter reset-guard effect: the guard raced the async cashAccounts/skvRows/transactions loads on every mount and wiped the restored choice back to 'Alla källor'.