P6: S3 blob store, Helm chart, air-gapped installer verify loop

- S3BlobStore (object_store, path-style) behind the same BlobStore trait,
  tested against a REAL MinIO container (round trip, overwrite, NotFound
  on get and delete, nested keys); [storage] backend=local|s3 config with
  validation + server-side selection (S3 creds via env overlay)
- Helm chart: server pod with the secret broker as a SIDECAR sharing a
  private emptyDir unix socket (no network hop carries credentials),
  frontend, optional local PVC vs S3, OIDC/oauth values, unbuffered-SSE
  ingress annotations, NetworkPolicies (frontend->server only), hardened
  securityContexts; ci/check-helm.sh lints AND asserts the rendered
  topology properties
- deploy/airgapped/install.sh: offline signature+checksum verification via
  the bundled teamclaw-bundler BEFORE any docker load; --verify-only mode;
  ci/test-install.sh rehearses clean/tampered/wrong-key paths with the
  real binary
- CI: helm gate + installer rehearsal wired in

149 Rust tests; helm lint + rendered assertions green; installer
verify-path rehearsal green.

Co-Authored-By: Claude Fable 5 <[email protected]>

crates/tc-files/Cargo.toml

@@ -8,10 +8,12 @@ publish.workspace = true
 
 [dependencies]
 async-trait = "0.1"
+object_store = { version = "0.12", features = ["aws"] }
 thiserror = { workspace = true }
 tokio = { workspace = true }
 
 [dev-dependencies]
+testcontainers-modules = { workspace = true }
 uuid = { workspace = true }
 
 [lints]