WP-30/31/32: backup targets, strategies and execution

SMB (smbclient) and FTP/FTPS (curl with netrc) targets with encrypted
credentials and connection test; strategies with cron schedule, retention,
optional openssl AES-256 encryption; sources: PVC hostpath tar, pg_dumpall
in the Postgres pod, namespace manifests, host directory. Backup job
collects, encrypts, uploads, verifies size, records sha256 and applies
retention on the target; scheduler starts due strategies. Backups page
with target/strategy forms, run now and history. Restore guide in docs.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

backend/crates/infrastructure/Cargo.toml

@@ -23,6 +23,7 @@ kube = { version = "0.99", default-features = false, features = ["client", "rust
 k8s-openapi = { version = "0.24", features = ["v1_32"] }
 
 [dev-dependencies]
+tempfile = "3"
 tokio.workspace = true
 
 [lints]