audit: Tier 0 quick wins — EMAIL_REDIRECT_TO prod guard + storage routing + metadata masking

Tier 0.2: src/lib/env.ts now refuses boot when NODE_ENV=production AND
EMAIL_REDIRECT_TO is set. Sendmail logs the rewrite at warn (was debug)
so dev/staging windows where someone forgets to unset are immediately
visible.

Tier 0.6: backup_jobs.storage_path added to TABLES_WITH_STORAGE_KEYS in
src/lib/storage/migrate.ts. Flipping the storage backend used to
silently orphan every pg_dump artefact — last-resort recovery path is
now actually portable.

Tier 1.7: createAuditLog now runs metadata through maskSensitiveFields
(was only applied to old/new value diffs). Portal-auth, crm-invite,
hard-delete and email-accounts services were writing raw emails into
this column unbounded.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/lib/audit.ts

@@ -143,7 +143,10 @@ export async function createAuditLog(params: AuditLogParams): Promise<void> {
       fieldChanged: params.fieldChanged ?? null,
       oldValue: maskSensitiveFields(params.oldValue) ?? null,
       newValue: maskSensitiveFields(params.newValue) ?? null,
-      metadata: params.metadata ?? null,
+      // Mask metadata too — the audit found portal-auth, crm-invite,
+      // hard-delete, and email-accounts services were writing raw emails
+      // into this column.
+      metadata: maskSensitiveFields(params.metadata) ?? null,
       ipAddress: params.ipAddress ?? null,
       userAgent: params.userAgent ?? null,
       severity,