both sidecars read their upstream from a new service_connections table instead of
process.env: one row per (user, service), the secret encrypted at rest, upserted
through a /_config route the app drives. transmission gains a Connection section,
soulseek gains one too, and both take over the whole app while nothing is stored.
TRANSMISSION_URL/USER/PASS/RPC_PATH and SLSKD_URL/API_KEY can come out of .env.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>