Feature requests from live use:
- "Daten aendern" was missing a "Wirksam ab" field (unlike Versetzen/
Befoerdern/Karenz, which all have one) - every change was silently
logged with today's date. Added the field, threaded through
change_employee_data (defaults to today if omitted).
- Staatsbuergerschaft and Wohnland now use a searchable picker
(components/ui/CountryPicker) over the full 193-country UN member
state list (lib/countries.ts) instead of the original ~9/5-value
picklists. Dropped the now-too-narrow CHECK constraints
(supabase/schema_2.sql) since the app is the source of truth for
valid values, same approach used elsewhere for large open-ended
pickers.
Two more real bugs found via live testing of the above (both in
change_employee_data, supabase/functions.sql + functions_4.sql):
1. `text[] || 'literal'` is ambiguous in Postgres - it can resolve to
the array||array overload and try to parse the plain word as array
syntax ('{...}'), failing with "malformed array literal". Hit on
every single field-diff line the moment a user actually changed
something (Staatsbuergerschaft first, then Beschaeftigungsausmass
confirmed the same root cause). Fixed everywhere by switching to the
unambiguous array_append() function.
2. The contract_end_date diff-check cast an empty string straight to
date ("invalid input syntax for type date: ''") instead of using the
same nullif(...,'')::date guard the UPDATE line below it already had.
Verified live end-to-end after both fixes: changed Staatsbuergerschaft
to Brasilien with a backdated effective date, save succeeded, Stammdaten
tab reflects it, and employee_history got the correct event_date
("2026-07-01") and description ("Geänderte Felder: Staatsbürgerschaft,
wirksam ab 2026-07-01"). Reverted the test employee's data back
afterward; seed data is clean again.
