feat(container): manifest-declared generated secrets + companion/quadlet hardening

Generated-secrets system: apps declare `generated_secrets` in their manifest
(kinds hex16/hex32/bcrypt); `container::secrets::ensure_generated_secrets`
materialises them 0600/rootless in resolve_dynamic_env — idempotent and
self-healing (recovers wrongly root-owned secrets with no privilege). Replaces
per-app Rust (deletes ensure_fmcd_password). fedimint-clientd/gateway manifests
now declare fmcd-password / fedimint-gateway-hash.

companion.rs: rebuild the auto-built :latest image when its build context changes
(staleness check) so baked-in fixes (e.g. guardian-UI CSS) actually reach nodes.

quadlet.rs: skip PublishPort under Network=host (podman rejects the combo, exit
125) + regression tests.

UI: "Fedimint Guardian" rename, fedimint-clientd/nostr-rs-relay/meshtastic tagged
as Services (headless backends), gateway icon fallback.

Deployed + verified on .228 (generated-secrets fixed fedimint-gateway start;
grafana/strfry orphan crash-loop units removed).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

apps/fedimint-gateway/manifest.yml

@@ -16,6 +16,14 @@ app:
         else
           exec gatewayd --data-dir /data --listen 0.0.0.0:8176 --bcrypt-password-hash "$FEDI_HASH" --network bitcoin --bitcoind-url http://host.archipelago:8332 --bitcoind-username "$FM_BITCOIND_USERNAME" --bitcoind-password "$FM_BITCOIND_PASSWORD" ldk --ldk-lightning-port 9737 --ldk-alias archipelago-gateway;
         fi
+    # The gateway's admin API is gated by a bcrypt password hash. Generate it on
+    # first install (random password + its bcrypt hash, both 0600 rootless-owned)
+    # so the app installs from its manifest alone — `fedimint-gateway-hash` holds
+    # the hash passed to gatewayd, `fedimint-gateway-hash.pw` the plaintext for
+    # any client that must authenticate. Self-heals a wrongly root-owned hash.
+    generated_secrets:
+      - name: fedimint-gateway-hash
+        kind: bcrypt
     secret_env:
       - key: FM_BITCOIND_PASSWORD
         secret_file: bitcoin-rpc-password