feat: extract .env validators to common.sh and add validate_env()

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>

CLAUDE.md

@@ -36,11 +36,14 @@ backup/               # Backup and restore scripts
 ## Key Commands
 - `setup/configure_env.sh` — Interactive .env setup wizard
 - `setup/cleanup.sh` — Reverse everything setup scripts installed (reads .manifests/)
-- `preflight.sh` — Validate everything before running phases
+- `preflight.sh` — Validate everything before running phases (includes .env format validation)
 - `run_all.sh` — Execute all phases sequentially
 - `teardown_all.sh` — Reverse teardown (add `--cleanup` to also uninstall prerequisites)
 - `manage_runner.sh add|remove|list` — Dynamic runner management
 
+## .env Validation
+`validate_env()` in `lib/common.sh` checks all ~50 .env variables against their expected format (IP, port, email, path, URL, bool, integer, password, ssl_mode). Uses parallel arrays for the variable-to-validator mapping (bash 3.2 compatible). Called by `preflight.sh` and `bitwarden_to_env.sh`. `configure_env.sh` uses the same individual validators interactively.
+
 ## Version Checking
 Setup scripts and preflight validate minimum versions for all tools:
 - Local: jq>=1.6, curl>=7.70, git>=2.30, shellcheck>=0.8, gh>=2.0