fix: remove duplicate rpcbind from bitcoin-knots container creation

bitcoin.conf already has server=1, rpcbind=0.0.0.0, rpcallowip, listen.
Passing them again via command-line causes bitcoin to try binding port
8332 twice → "Address already in use" → container crashes on every start.

Now only passes pruning/txindex args and dbcache via CLI.
Health check uses cookie auth (-datadir) instead of plaintext password.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

scripts/first-boot-containers.sh

@@ -400,10 +400,8 @@ if ! $DOCKER ps --format '{{.Names}}' 2>/dev/null | grep -qE 'bitcoin-knots|arch
     -p 8332:8332 -p 8333:8333 -p 28332:28332 -p 28333:28333 \
     -v /var/lib/archipelago/bitcoin:/home/bitcoin/.bitcoin \
     "${BITCOIN_KNOTS_IMAGE}" \
-    -server=1 $BTC_EXTRA_ARGS \
-    -rpcallowip=0.0.0.0/0 -rpcbind=0.0.0.0:8332 \
-    -proxy=host.containers.internal:9050 -listen=1 -bind=0.0.0.0:8333 \
-    -dbcache=$BTC_DBCACHE 2>>"$LOG"; then
+    $BTC_EXTRA_ARGS \
+    -printtoconsole=1 -dbcache=$BTC_DBCACHE 2>>"$LOG"; then
     log "Bitcoin Knots started"
   else
     log "Bitcoin Knots failed (may already exist)"