Stop the seed handing out addresses that look like real ones

Every employee address in the database sat on test.manner.at, a domain
that reads like a company one. employees.email is the *private* address,
so an address shaped like a company mailbox invites being taken for one
— and eventually being written to. All 856 rows now sit on
privat.alpenwerk-test.at, rebuilt from first and last name, and the seed
generates the same domain so a reseed does not bring the old one back.

Umlauts are spelled out the way they are here (Höller becomes hoeller),
other accents are flattened, and where two people share a name the
personnel number is appended.

The first attempt got this wrong in a way worth recording. It wrote
ma<number>@ for all 856 rows instead of the intended name form, and the
check I had built only asked whether the results were unique and
well-formed — which they were. Two defects, both invisible to that
check: '\.+' inside a SQL literal was read as "any character, one or
more" and collapsed the whole local part to a single dot, and the
replacement string for the accent mapping had one character too many, so
the mapping was shifted. The fix uses '[.]+', a character class needing
no escape at all, so it no longer depends on how the connection treats
backslashes.

Untouched on purpose: app_users.email and profiles.email are the sign-in
accounts, and rewriting those would lock people out.

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

supabase/seed.ts

@@ -380,12 +380,18 @@ type HistoryRow = {
 
 const usedEmails = new Set<string>();
 
+// Eine Domain, die niemandem gehört und offensichtlich keine echte ist.
+// `employees.email` ist die *private* Adresse; eine erfundene Testdomain, die
+// wie eine Firmenadresse aussieht, lädt dazu ein, sie für eine zu halten —
+// und im schlimmsten Fall, an sie zu schreiben.
+const MAIL_DOMAIN = "privat.alpenwerk-test.at";
+
 function makeEmail(firstName: string, lastName: string): string {
   const base = `${slugify(firstName)}.${slugify(lastName)}`;
-  let email = `${base}@test.manner.at`;
+  let email = `${base}@${MAIL_DOMAIN}`;
   let n = 2;
   while (usedEmails.has(email)) {
-    email = `${base}${n}@test.manner.at`;
+    email = `${base}${n}@${MAIL_DOMAIN}`;
     n += 1;
   }
   usedEmails.add(email);