Fix OAuth state validation by enabling int64 mode in local SQLite
JavaScript timestamps (milliseconds since epoch) are larger than 32-bit integers can hold.
Without int64 mode, Deno SQLite truncates these to signed 32-bit values, causing negative timestamps.
This caused OAuth state lookups to fail because DrizzleStorage's expiration check (expires_at > now)
would compare negative values against current timestamps.
Solution: Enable int64 mode in Database constructor to properly store 64-bit INTEGER values.
Also improved DEVELOPMENT.md OAuth setup instructions.