fix xlab-gateway host key in secrets.nix and rekey ...

The active host key on xlab-gateway is the original one
(AAAAII+EKDpU...), not the replacement. Corrected and rekeyed.

Co-Authored-By: Claude Opus 4.6 (1M context) <[email protected]>

add ylw ed25519 key: agenix access, SSH auth, rekey all secrets ...

- Add ylw's ed25519 public key to secrets.nix admins list
- Re-encrypt all .age secrets so ylw can decrypt
- Add ed25519 key to ye-lw21 authorized SSH keys

Co-Authored-By: Claude Opus 4.6 (1M context) <[email protected]>

skydick: add Telegraf monitoring with SMART, ZFS, and system metrics ...

Sends metrics to door1 InfluxDB (bucket: skydick) via Telegraf.
Monitors all 5 Mach2 SAS drives, NVMe P4500, and boot SSD via SMART.
InfluxDB token encrypted with agenix.

Co-Authored-By: Claude Opus 4.6 <[email protected]>