Hotfix: DB connection on Supabase transaction pooler (port 6543)

[immerSIR]

Prod outage fix — 502 on all endpoints after #43

Root cause (from live container logs):

OperationalError: connection to "db.nwzsmdbyjmjzhruguwrb.supabase.co", port 6543 failed:
FATAL: unsupported startup parameter: options

Prod connects via the Supabase transaction pooler (6543), which rejects the libpq options startup parameter. Our settings set search_path=public through exactly that parameter, so every DB connection was refused → migrate/daphne died → 502.

Fix: don't send the options param on the 6543 pooler. The Supabase postgres role already has public before extensions in its default search_path, and all app tables live in public, so schema resolution is correct without it. Session-pooler/direct/local connections (dev, CI) still send options unchanged. Escape hatch: DB_SET_SEARCH_PATH=true|false.

One file, backwards-compatible. Merging redeploys and restores prod.