Test data with `@virastack/mask/testing`, and a plate preset

• New @virastack/mask/testing entry: Test and seed data generators. The root and /server entries don't export them, so they never reach production bundles. No React and no "use client", about 2 KB.
• generateTCKN(): A TCKN that passes isValidTCKN. No list is kept; every number is made on the spot.
• generateIBAN(country, { bank }): Turkish IBANs follow the national layout with a bank from turkishBanks; bank: "0062" picks Garanti. Every country in the IBAN registry works, with a digits-only account part that passes isValidIBAN.
• seed option: An integer seed gives the same value on every run and platform, so snapshots and seed data stay stable.
• plate preset and isValidPlate(): Shows 34 ABC 123, stores 34ABC123. Province code 01–81, then 1 letter and 4–5 digits, 2 letters and 3–4 digits, or 3 letters and 2–3 digits, from article 34 of the vehicle registration regulation. Name plates and special plates are not checked.
• Smaller bank-only bundles: Importing only getTurkishBank no longer pulls in every preset; it drops from 2.3 KB to under 1 KB.

Tests and seed scripts kept copying the same few example numbers, and a hand-made TCKN or IBAN usually fails the checksum. A generated value can belong to a real person or account, so the generators are for tests and seed data only.