Harden deployment: DB ownership and config secrecy

- Restrict the deployed /etc/esim-provisioning/config.yaml to 600 owned by the
  esim service user; it holds the OP key and was previously world-readable.
- Chown data/ AFTER init_db runs (as root) so the SQLite file is owned by the
  esim service user; the service runs with ReadWritePaths=.../data and could
  not write a root-owned database before.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

CHANGELOG.md

@@ -33,6 +33,11 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - The in-memory profile cache is guarded by a lock (thread-safe under a
   threaded server), and the captive portal disables the activate button while
   a request is in flight to prevent double provisioning.
+- `setup_wifi_ap.sh`: the deployed `config.yaml` (holds the OP key) is now
+  `chmod 600` and owned by the service user instead of world-readable, and
+  `data/` is chowned *after* `init_db` so the root-created SQLite file is
+  writable by the `esim` service (previously it was root-owned and the service
+  could not write to it).
 - Added `test_app.py` (API-level: provision, rate-limit, token download,
   404 on unknown/enumerated ids, collision retry/give-up), `test_utils.py`
   (MAC/IMSI/op_key/config/ensure_parent_dir), and adapter APN coverage.

scripts/setup_wifi_ap.sh

@@ -143,8 +143,12 @@ python3 -m venv "$INSTALL_DIR/venv"
 # Create system user
 id esim &>/dev/null || useradd --system --no-create-home --shell /usr/sbin/nologin esim
 
+# Restrict config — it holds the OP key and other secrets. Readable only by
+# the service user, not world-readable.
+chown esim:esim /etc/esim-provisioning/config.yaml
+chmod 600 /etc/esim-provisioning/config.yaml
+
 mkdir -p "$INSTALL_DIR/data"
-chown -R esim:esim "$INSTALL_DIR/data"
 
 # Install systemd services
 cp "$REPO_DIR/systemd/esim-provisioning.service" /etc/systemd/system/
@@ -155,6 +159,10 @@ systemctl daemon-reload
 CONFIG_PATH=/etc/esim-provisioning/config.yaml \
     "$INSTALL_DIR/venv/bin/python" "$INSTALL_DIR/scripts/init_db.py"
 
+# Own data (incl. the DB file just created by root) as the service user, which
+# runs with ReadWritePaths=.../data — otherwise the service cannot write it.
+chown -R esim:esim "$INSTALL_DIR/data"
+
 # Enable everything
 systemctl unmask hostapd
 systemctl enable hostapd dnsmasq nginx esim-provisioning captive-portal