Remove Supabase

The database moved to a container of our own; the platform is gone.
This takes out what was left of it — and, where the leftovers were load
bearing, moves rather than deletes.

Moved, not deleted:

  supabase/migrations/  -> db/migrations/      the schema's source of truth
  supabase/build-org.ts -> scripts/build-org.ts
  lib/supabase/types.ts -> lib/types.ts        52 import sites repointed

The bookkeeping needed care. It lived in `supabase_migrations.schema_migrations`,
and simply renaming the schema would have left the runner facing an empty
table: it would have called all 67 migrations pending and replayed them
against a database that is long since current. So the runner now creates
`migrationen.schema_migrations` and, once, copies the old rows across —
guarded so a second run does nothing and a fresh database skips it entirely.
Only then does migration 20260907100000 drop the old schema.

Deleted: the CLI config, the seed, the historical schema/function dumps
(nothing read them), scripts/umzug-von-supabase.sh (the move is done), and
both Supabase packages plus the CLI. Nothing in the application imported
them — the build now succeeds with no environment variables at all, which
is the proof.

Integration tests: six of them signed in through Supabase Auth and asserted
against the anon key and the service role. That model is gone, so the tests
were not portable — they are deleted. session-context and
employee-status-filter already ran on pg and are untouched; om-reporting is
ported to a direct connection because it guards a real risk (the reporting
line rule exists twice, once in SQL and once in TypeScript).

CI: the integration job started a Supabase stack. It now runs a postgres
service, applies deploy/db-init and every migration to an empty database —
that was the valuable part, and it still holds — then checks that a second
run is a no-op, which is what proves the bookkeeping works.

Docs: security-review.md audited a service-role key, a cookie adapter and
auth.users, none of which exist. Restating findings about removed components
would suggest today's system had been reviewed; it has not. It now records
what was removed and says a fresh review is due. data-model.md was already
marked obsolete and described the pre-OM schema; azure-migration.md was a
plan for a route not taken. Both deleted.

Verified: npm ci, typecheck, lint, 445 tests, build — all clean without the
packages. Integration tests skip cleanly with no database. Migration SQL and
the runner are reviewed but NOT executed: no Docker here, and the old
instance no longer resolves.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

db/migrations/20260810130000_fix_rehire_status_cast.sql

@@ -0,0 +1,65 @@
+-- rehire_employee funktionierte nie.
+--
+--     status = case when v_date <= current_date then 'Aktiv' else 'Geplant' end
+--
+-- Der case-Ausdruck ist `text`, die Spalte ist `employment_status`. Postgres
+-- weist das ab:
+--
+--     column "status" is of type employment_status but expression is of type text
+--
+-- Sichtbar wurde es erst jetzt. Davor brach die Funktion eine Zeile früher ab,
+-- weil das Formular nie eine Planstelle mitschickte — ein Fehler verdeckte den
+-- anderen, wie schon bei hire_employee.
+--
+-- Bei den beiden anderen Zuweisungen im selben update (exit_date, exit_reason)
+-- stellt sich die Frage nicht: `null` ist typunabhängig.
+
+do $$
+declare
+  v_def text;
+  v_neu text;
+begin
+  select pg_get_functiondef(p.oid) into v_def
+    from pg_proc p
+    join pg_namespace n on n.oid = p.pronamespace
+   where n.nspname = 'public' and p.proname = 'rehire_employee'
+   limit 1;
+
+  v_neu := regexp_replace(
+    v_def,
+    '(case\s+when\s+v_date\s*<=\s*current_date\s+then\s+''Aktiv''\s+else\s+''Geplant''\s+end)',
+    '(\1)::employment_status',
+    'g'
+  );
+
+  if v_neu = v_def then
+    raise exception 'Das Muster für den Status passte nicht — rehire_employee blieb unverändert.';
+  end if;
+
+  execute v_neu;
+end;
+$$;
+
+-- ═══ Gegenprobe ══════════════════════════════════════════════════
+-- Nachgestellt wird die **Spaltenzuweisung**, nicht die an eine Variable.
+-- Das ist der Unterschied, an dem mein erster Prüfausdruck vorbeiging:
+-- plpgsql wandelt bei einer Variablenzuweisung stillschweigend um, ein
+-- UPDATE auf eine Spalte nicht. Nur die zweite Form entspricht dem Fehler.
+do $$
+begin
+  create temp table probe_status (s employment_status) on commit drop;
+  insert into probe_status values ('Aktiv');
+
+  begin
+    execute $probe$ update probe_status set s = (case when true then 'Aktiv' else 'Geplant' end)::text $probe$;
+    raise exception 'Eine text-Zuweisung an eine employment_status-Spalte wirft nicht mehr — die Prüfung ist wertlos geworden.';
+  exception
+    when datatype_mismatch then null;  -- erwartet
+  end;
+
+  execute $probe$ update probe_status set s = (case when true then 'Aktiv' else 'Geplant' end)::employment_status $probe$;
+  if (select s from probe_status) <> 'Aktiv'::employment_status then
+    raise exception 'Die umgewandelte Form liefert nicht Aktiv.';
+  end if;
+end;
+$$;