[Task]: Configuration, docs and samples

Description

The README and the sample still described a Harbor deployed per namespace and a RegistryBackend CRD that no longer exists and documented environment variables
Configuration also let HARBOR_URL use http silently while the client sends the Harbor password as Basic Auth on every request.

Acceptance criteria

1. README sample and API doc comments describe one shared Harbor , global project names, and the two credential Secrets.
2. Only the variables the operator actually reads are documented- HARBOR_URL, POD_NAMESPACE, HARBOR_CREDENTIALS_SECRET, METRICS_CERT_DIR.
3. HARBOR_URL refuses http unless an explicit opt-in is set and the operator reports it on every start while it is.
4. Documented: how to copy a pull Secret to another cluster and which fields to strip.

Verification

No reference to a removed variable or to RegistryBackend remains outside git history.

Locate the README, sample manifests, API doc comments, and the operator’s configuration and startup handling. Compare documented variables with those actually read, then trace HARBOR_URL validation and startup reporting. Verify completion by searching for removed variables and RegistryBackend outside git history and checking the credential Secret-copy guidance.