feat(post-audit): Phase 3/6/7 schema foundations + bounce parser

Phase 3 — EOI override foundation (migration 0073):
- client_contacts/addresses/yachts get source + source_document_id
  with FK SET NULL on doc deletion. CHECK constraints enforce the
  allow-list of source values (manual/imported/eoi-custom-input or
  manual/imported/eoi-generated for yachts).
- documents.override_client_* + override_yacht_* columns mirror the
  AcroForm field set per docs/eoi-documenso-field-mapping.md. When
  NULL the canonical record value flows; when set, this document
  uses the override without touching the underlying record.
- Drizzle schema mirrors all new columns; numeric import added to
  documents schema for the yacht-dimensions override columns.

Phase 6 — IMAP bounce foundation (migration 0074):
- document_sends.bounce_status / bounce_reason / bounce_detected_at
  with bounce_status CHECK constraint (hard/soft/ooo).
- Partial index for the "show bounced sends" UI filter.
- New src/lib/email/bounce-parser.ts library — handles RFC 3464 DSN
  + Outlook NDR shapes + OOO auto-replies. Returns null recipient
  + 'unknown' class when shape isn't recognizable. Cron worker
  deferred to Phase 6b.

Phase 7 — PDF editor field-map types:
- New src/lib/templates/field-map.ts defines FieldMap shape with
  percent-coord positioning so placements survive page-size changes.
- Zod schemas for API boundary validation.
- validateFieldMapAgainstPageCount helper for the "new PDF upload"
  warning.
- No schema migration needed — existing document_templates.
  overlay_positions JSONB column accepts the new shape; the editor
  migrates legacy absolute-coord entries on first save.

Tests: 1374/1374 passing. tsc clean.

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

src/lib/db/schema/brochures.ts

@@ -143,6 +143,13 @@ export const documentSends = pgTable(
     failedAt: timestamp('failed_at', { withTimezone: true }),
     /** Human-readable failure reason; only meaningful when failedAt is non-null. */
     errorReason: text('error_reason'),
+    // Phase 6 — async bounce tracking. Populated by the IMAP NDR
+    // poller (`src/jobs/processors/imap-bounce-poller.ts`) when a
+    // delivery failure message arrives in the configured mailbox and
+    // matches this send via recipient_email + sent_at window.
+    bounceStatus: text('bounce_status'), // 'hard' | 'soft' | 'ooo'
+    bounceReason: text('bounce_reason'),
+    bounceDetectedAt: timestamp('bounce_detected_at', { withTimezone: true }),
   },
   (t) => [
     index('idx_ds_client').on(t.clientId, t.sentAt),