fix(migration): NocoDB import safety + dedup helpers + lead-source backfill

migration-apply: residential client + interest inserts now wrap in
db.transaction so a partial failure can't leave an orphan client
row without its interest (or vice versa).

migration-transform: buildPlannedDocument returns null when there
are no signers so the apply pass doesn't try to send a Documenso
envelope without recipients. mapDocumentStatus gets an explicit
"Awaiting Further Details" branch that no longer auto-promotes via
stale sign-time fields. parseFlexibleDate handles ISO and DD-MM-YYYY
inputs uniformly.

backfill-legacy-lead-source: chunk UPDATE WHERE clause now
isNull(source) on top of the inArray match, so a re-run can't
overwrite a more accurate source written between batches.

Adds 235 lines of vitest coverage on migration-transform.

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

src/lib/dedup/nocodb-source.ts

@@ -7,7 +7,7 @@
  *
  * Auth: `xc-token` header per NocoDB v2 API.
  *
- * The shape returned is a verbatim record of the row's fields — caller
+ * The shape returned is a verbatim record of the row's fields - caller
  * is responsible for mapping to the new schema via `nocodb-transform.ts`.
  */
 
@@ -34,7 +34,7 @@ export function loadNocoDbConfig(env: NodeJS.ProcessEnv = process.env): NocoDbCo
 
 // ─── Table identifiers ──────────────────────────────────────────────────────
 //
-// These IDs are stable per the NocoDB base — they were captured during the
+// These IDs are stable per the NocoDB base - they were captured during the
 // 2026-05-03 audit and won't change unless the base is rebuilt. If the
 // base is reset, regenerate them from `getTablesList`.
 export const NOCO_TABLES = {
@@ -67,7 +67,7 @@ export type NocoDbRow = Record<string, unknown> & { Id: number };
 /**
  * Fetch all rows from a NocoDB table. Auto-paginates until the API
  * reports `isLastPage`. The legacy base is small (252 Interests rows
- * being the largest table) so we keep this simple — no streaming.
+ * being the largest table) so we keep this simple - no streaming.
  */
 export async function fetchAllRows(
   tableId: string,
@@ -95,7 +95,7 @@ export async function fetchAllRows(
 
     if (!res.ok) {
       throw new Error(
-        `NocoDB fetch failed: ${res.status} ${res.statusText} — table ${tableId} page ${page}`,
+        `NocoDB fetch failed: ${res.status} ${res.statusText} - table ${tableId} page ${page}`,
       );
     }
 
@@ -110,7 +110,7 @@ export async function fetchAllRows(
 }
 
 /**
- * Convenience snapshot — pulls every table the migration cares about
+ * Convenience snapshot - pulls every table the migration cares about
  * in parallel. Returned shape is the input the transform layer expects.
  */
 export interface NocoDbSnapshot {