feat: implement fiscal period date fields component and validation logic (#301)

* feat: implement fiscal period date fields component and validation logic

* feat: update fiscal period validation and naming logic

supabase/migrations/20260421132742_backfill_sie_opening_balance_links.sql

@@ -0,0 +1,36 @@
+-- Backfill fiscal_periods.opening_balance_entry_id for periods where a SIE
+-- import created an opening-balance journal entry but never linked it back to
+-- the period. Without the link, getOpeningBalances falls through to summing
+-- all prior journal-entry lines before period_start, which double-counts each
+-- year's IB against the prior year's UB and inflates balance-sheet accounts
+-- in proportion to the number of years imported.
+--
+-- Safe to re-run: only periods with NULL opening_balance_entry_id are updated.
+-- The enforce_opening_balance_immutability trigger (migration 019) only fires
+-- when OLD.opening_balance_entry_id IS NOT NULL, so this UPDATE is permitted.
+--
+-- Periods with more than one posted opening-balance entry (should not happen
+-- because checkDuplicatePeriodImport rejects overlapping imports, but a failed
+-- partial import could theoretically produce this) are intentionally skipped
+-- so the correct entry can be chosen manually rather than linked arbitrarily.
+
+UPDATE public.fiscal_periods fp
+SET
+  opening_balance_entry_id = (
+    SELECT je.id
+    FROM public.journal_entries je
+    WHERE je.fiscal_period_id = fp.id
+      AND je.company_id = fp.company_id
+      AND je.source_type = 'opening_balance'
+      AND je.status = 'posted'
+    LIMIT 1
+  ),
+  opening_balances_set = true
+WHERE fp.opening_balance_entry_id IS NULL
+  AND (
+    SELECT COUNT(*) FROM public.journal_entries je
+    WHERE je.fiscal_period_id = fp.id
+      AND je.company_id = fp.company_id
+      AND je.source_type = 'opening_balance'
+      AND je.status = 'posted'
+  ) = 1;