Fixes cache initialization failures on unencrypted repositories and
standardizes environment variable configuration across all backup jobs.
Changes:
- Add BORG_UNKNOWN_UNENCRYPTED_REPO_ACCESS_IS_OK to unencrypted repos
  (fuchsia/viridian onsite) to bypass interactive confirmation prompt
- Refactor all environment.BORG_RSH to multiline attribute set format
  for consistency and future extensibility
The cache initialization error occurred after removing persistent timers
(commit 
		
	
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|---|---|---|
| .. | ||
| multimedia | ||
| services | ||
| configuration.nix | ||
| hardware-configuration.nix | ||
| ssh_host_ed25519_key.pub | ||
| ssh_host_rsa_key.pub | ||