feat(cli): automation bundle + identity-minimization features

Reduces manual setup steps and trims user-identifying data exposed by the
server/client, in the spirit of the deployment story: an operator on the
wire sees less, and the admin types fewer commands.

New CLI subcommands:
- `aura server-init`: one shot — pki init + issue-server + writes a ready
  server.toml with auto-detected egress iface; flags --enable-knock,
  --enable-cover-traffic, --no-nat, --run-as toggle the new transport
  defenses and privilege drop.
- `aura provision-client`: issues a client cert and assembles the full
  bundle (ca.crt + client.crt + client.key + client.toml in one directory)
  ready to hand over to the client device. --id is optional (defaults to
  a fresh UUIDv4, so client identities don't have to encode anything real).

Identity / log minimization:
- `aura pki issue-client --id` is now optional — UUIDv4 by default.
- `[server]/[client] no_logs = true` filters peer_id, client_ip,
  source_addr, client_id, local_ip, user, id, assigned_ip, peer field
  values through a custom tracing FormatFields layer (events still fire
  but the identifying fields are redacted before being written).
- `[client] bridges = [...]`: secondary server addresses; build_dial_targets
  shuffles them after the primary, so blocking one IP doesn't kill the
  client.
- Auto-detect egress iface in [server.nat] (via detect_default_egress_iface);
  egress_iface in config becomes optional with graceful fallback.

Config examples updated; backward-compatible (all new sections optional with
serde defaults). Workspace: 207 tests passed (+22), clippy -D warnings clean,
fmt clean. No new workspace deps.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

config/client.toml.example

@@ -15,6 +15,14 @@ sni = "cdn.example.com"
 # no-op (use a service account instead). When omitted (or already running as non-root) no
 # privilege change happens.
 # run_as = "nobody"
+# Suppress identifier fields (peer_id, client_ip, source_addr, ...) from log output. The events
+# still fire; only the identifying fields are dropped before formatting. Default: false. Set to
+# true to keep the local log file from accumulating per-session identifiers.
+no_logs = false
+# Optional fallback server addresses (IP or IP:port). When the primary `server_addr` cannot be
+# reached on any transport, the client retries the bridges in a process-randomised order, using
+# the same per-transport ports from [transport]. The bridge `:port` part is parsed but ignored.
+# bridges = ["203.0.113.11", "203.0.113.12"]
 
 [pki]
 # Trust anchor (the Aura CA) and this client's leaf cert/key, all PEM.
@@ -107,3 +115,14 @@ masquerade = true
 # Existing connections keep the mask they connected with. Default: true.
 # When `false`, the static values above ([client] sni, [transport] obfuscate, ...) are used as-is.
 enabled = true
+
+[transport.knock]
+# UDP port-knocking. Must match the server's setting. Default: false.
+enabled = false
+knock_secret_source = "ca_fingerprint"
+
+[transport.cover]
+# Idle-time cover traffic. Must match the server's setting. Default: false.
+enabled = false
+mean_interval_ms = 500
+jitter = 0.5