Replace mapdns with daemon DNS

Serve daemon-managed .vm names directly from bangerd on 127.0.0.1:42069 instead of shelling out to mapdns. This keeps DNS state tied to VM lifecycle and lets the daemon rebuild records from running VMs after startup or reconcile.

Add a small in-process authoritative DNS server, register and remove records from the VM start/stop/delete paths, and show the listener in daemon status. Remove the mapdns config and preflight surface, stop helper-flow DNS publishing in customize.sh and interactive.sh, drop dns.sh from the runtime bundle, and update docs/tests for the new local-resolver integration model.

Validated with GOCACHE=/tmp/banger-gocache go test ./..., GOCACHE=/tmp/banger-gocache make build, and bash -n customize.sh interactive.sh.

customize.sh

@@ -40,7 +40,6 @@ if [[ ! -d "$RUNTIME_DIR" ]]; then
   log "run 'make runtime-bundle' or set BANGER_RUNTIME_DIR"
   exit 1
 fi
-source "$RUNTIME_DIR/dns.sh"
 source "$RUNTIME_DIR/packages.sh"
 STATE="${BANGER_STATE_DIR:-${XDG_STATE_HOME:-$HOME/.local/state}/banger/image-build}"
 VM_ROOT="$STATE/vms"
@@ -235,7 +234,6 @@ mkdir -p "$VM_DIR"
 API_SOCK="${XDG_RUNTIME_DIR:-/run/user/$(id -u)}/banger/fc-$VM_TAG.sock"
 LOG_FILE="$VM_DIR/firecracker.log"
 TAP_DEV="tap-fc-$VM_TAG"
-DNS_NAME=""
 
 # Allocate guest IP
 NEXT_IP_FILE="$STATE/next_ip"
@@ -252,7 +250,6 @@ cleanup() {
   fi
   sudo ip link del "$TAP_DEV" 2>/dev/null || true
   rm -f "$API_SOCK"
-  banger_dns_remove_record_name "${DNS_NAME:-}"
   rm -rf "$VM_DIR"
 }
 trap cleanup EXIT
@@ -340,8 +337,6 @@ fi
 
 VM_CONFIG_JSON="$(sudo -E curl --unix-socket "$API_SOCK" -sS http://localhost/vm/config)"
 CREATED_AT="$(date -Iseconds)"
-DNS_NAME="$(banger_dns_name "$VM_NAME")"
-banger_dns_write_record "$VM_NAME" "$GUEST_IP"
 jq -n \
   --arg id "$VM_ID" \
   --arg name "$VM_NAME" \
@@ -353,9 +348,8 @@ jq -n \
   --arg log "$LOG_FILE" \
   --arg rootfs "$OUT_ROOTFS" \
   --arg kernel "$KERNEL" \
-  --arg dns_name "$DNS_NAME" \
   --argjson config "$VM_CONFIG_JSON" \
-  '{meta:{id:$id,name:$name,pid:$pid,created_at:$created_at,guest_ip:$guest_ip,tap:$tap,api_sock:$api_sock,log:$log,rootfs:$rootfs,kernel:$kernel,dns_name:$dns_name},config:$config}' \
+  '{meta:{id:$id,name:$name,pid:$pid,created_at:$created_at,guest_ip:$guest_ip,tap:$tap,api_sock:$api_sock,log:$log,rootfs:$rootfs,kernel:$kernel},config:$config}' \
   > "$VM_DIR/vm.json"
 
 log "enabling NAT for customization"