feat(nostr-vpn): package paid-exit seller + web control panel as manifest apps

Phase 1 of docs/nostr-vpn-integration-plan.md's Phase 0->4 plan (seller-side
rootless feasibility already confirmed there). Two apps, one image:

- apps/nostr-vpn: the daemon. Own network namespace (container.network:
  pasta), NET_ADMIN+NET_RAW scoped to that netns, /dev/net/tun, and the
  net.ipv4.ip_forward sysctl via the primitive added in e42bd26. UDP 51822
  (not upstream's default 51820, which collides with archipelago-wg on
  fleet nodes per the Phase 0 log). Seller mode stays off until an operator
  explicitly enables it (paid_exit.enabled defaults to false upstream).
- apps/nostr-vpn-web: the control panel, gated behind 127.0.0.1:38080,
  talking to the daemon only through the shared /data volume (state-file
  status + shelling out to the nvpn CLI) -- no network link between the
  two containers, matching upstream's own umbrel/docker-compose.yml.
- docker/nostr-vpn: upstream's umbrel/Dockerfile, unchanged except for how
  the pinned commit arrives (shallow git fetch of a verified SHA, since
  codeload.github.com archive tarballs 404 from this environment and
  GitHub won't fetch an arbitrary SHA directly). Entrypoint seeds a minimal
  config.toml with the chosen listen_port on first boot only -- every
  AppConfig field is `serde(default = ...)`, confirmed by reading
  nostr-vpn-core directly, so this merges with nvpn's own identity/wallet
  bootstrap instead of needing a generated_secrets entry or full config
  template, and never touches a config that already exists.

Both volumes point at /var/lib/archipelago/nostr-vpn, adopting state from
the old root-mode install. Build and the seed-config path were verified
against the real `nvpn daemon` binary, not just read -- see the plan doc's
Phase 1 log for what that caught (a fabricated commit SHA, the codeload
404, wrong default branch name, and confirming identity/wallet persistence
actually survives container recreation).

Not done here, flagged in the plan doc instead: removing the old root-mode
path (rpc/vpn.rs, rpc/auth.rs's auto-enable-on-login) touches live
onboarding on every node, not just this app -- needs explicit sign-off.
Also missing: a stop-hook/uninstall-guard manifest primitive (doesn't
exist yet -- LifecycleHooks only has post_install/pre_start) for the
collect-due-on-stop and non-zero-wallet uninstall guard, and registry
mirroring + catalog signing (need credentials this pass doesn't have).

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

docker/nostr-vpn/docker-entrypoint.sh

@@ -0,0 +1,37 @@
+#!/bin/sh
+# Shared entrypoint for both apps/nostr-vpn (daemon) and apps/nostr-vpn-web
+# (control panel) -- they're the same image, differing only in the args
+# this script execs into (see each manifest's container.entrypoint/custom_args).
+#
+# Seeds a minimal config.toml with our chosen listen_port BEFORE nvpn's own
+# bootstrap (config_bootstrap.rs::load_or_default_config) ever runs, so the
+# very first boot never has to self-heal off upstream's default 51820 --
+# archy-x250 fleet nodes already run archipelago-wg on that port (found in
+# Phase 0 testing, see docs/nostr-vpn-integration-plan.md). Every AppConfig
+# field has #[serde(default = ...)], confirmed by reading
+# crates/nostr-vpn-core/src/config/types.rs directly, so a partial TOML here
+# merges cleanly with nvpn's own defaults (including the self-generated
+# Nostr seller identity) instead of needing a full config.
+#
+# Never overwrites an existing config.toml: this volume may already hold a
+# seller's identity, wallet, and pending Cashu credit adopted from the old
+# root-mode install (/var/lib/archipelago/nostr-vpn) -- clobbering it would
+# be a real funds-safety bug, not just a config reset.
+set -eu
+
+NVPN_LISTEN_PORT="${NVPN_LISTEN_PORT:-51822}"
+CONFIG_DIR=/data/config/nvpn
+CONFIG_PATH="$CONFIG_DIR/config.toml"
+
+mkdir -p "$CONFIG_DIR" /data/home
+
+if [ ! -f "$CONFIG_PATH" ]; then
+  cat > "$CONFIG_PATH" <<EOF
+[node]
+listen_port = ${NVPN_LISTEN_PORT}
+EOF
+  chmod 600 "$CONFIG_PATH"
+  echo "nostr-vpn: seeded $CONFIG_PATH with listen_port=${NVPN_LISTEN_PORT} (first boot)"
+fi
+
+exec "$@"