feat: v1.6.4 release

[cody-rester]

Summary

• Bug fixes and security hardening (manual capture NameError, Vault silent failures, kubectl pod targeting, credential warning in kubectl env)
• New Dracula theme added to the theme registry
• diff.html rethemed to match report.html light/dark system
• --version output updated to show structured version, build, Python, and OS info
• Build number added to _version.py

Changes

• BUG-1/SEC-1: Fixed NameError crash in --manual capture mode (log_since_str/log_until_str uninitialized)
• SEC-2: kubectl exec printenv consent prompt now explicitly warns that captured values include credentials
• SEC-5: credential_store() no longer silently swallows invalid credential_backend config values
• SEC-6: Vault _read_all() now raises CredentialError on token expiry/read failure instead of returning {}; adds per-session caching
• BUG-5: _find_iap_pod() no longer falls through to an unlabeled kubectl get pods query
• Added ATLAS_DRACULA theme and registered as "dracula" in THEME_REGISTRY
• diff.html updated to full light/dark theme system matching report.html
• --version now shows version, build, python, and os fields