feat(db): tighten chk_system_folder_shape, add recommender FK + composite indexes

- Fix A5: chk_system_folder_shape NULL escape
- Fix Audit 17 G-I4: berthRecommendations.interestId FK with cascade
- Add (port_id, client_id) / (port_id, company_id) / (port_id, yacht_id) composite indexes on files + documents for aggregated-projection performance

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

src/lib/db/schema/berths.ts

@@ -14,6 +14,7 @@ import {
 import { ports } from './ports';
 import { clients } from './clients';
 import { yachts } from './yachts';
+import { interests } from './interests';
 
 export const berths = pgTable(
   'berths',
@@ -131,7 +132,9 @@ export const berthRecommendations = pgTable(
     id: text('id')
       .primaryKey()
       .$defaultFn(() => crypto.randomUUID()),
-    interestId: text('interest_id').notNull(), // references interests.id
+    interestId: text('interest_id')
+      .notNull()
+      .references(() => interests.id, { onDelete: 'cascade' }),
     berthId: text('berth_id')
       .notNull()
       .references(() => berths.id, { onDelete: 'cascade' }),