Move 10 validation functions from configure_env.sh to lib/common.sh as
shared utilities. Define variable-to-validator mapping using parallel
arrays (bash 3.2 compatible). validate_env() checks all ~50 .env
variables against their expected format and reports all failures at once.
Wired into preflight.sh (Check 6b) and bitwarden_to_env.sh (post-restore).
configure_env.sh now sources validators from common.sh instead of
defining its own copies.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
