feat: support configurable Cloudflare secret key names

[russell-parks]

Summary

• add camelCase Cloudflare secret key fields (apiTokenKey, apiKeyKey, emailKey) with defaults that preserve current behavior
• keep the existing uppercase fields as legacy aliases and resolve precedence so old manifests continue to work
• update controller secret lookup, CRD schemas, tests, and auth docs/examples for configurable secret data keys

Testing

• GOTOOLCHAIN=go1.24.2 GOCACHE=/private/tmp/cloudflare-operator-go-build GOMODCACHE=/private/tmp/cloudflare-operator-go-mod /opt/homebrew/bin/go test ./api/v1alpha1 ./api/v1alpha2 ./internal/controller -count=1

[adyanth]

Thanks for the contribution! Could you please run the golangci-linter and fix them please? The PR looks good to me.

[russell-parks]

Done, thanks. I pushed 99971c2 to wrap the long log line reported by golangci-lint.\n\nLocal validation:\n- make lint -> 0 issues\n- go test ./... -> passed\n\nRemediation checkpoint: CFOP-PR183-LINT-001 against prior head 8111326.