refactor(interests): migrate callers to interest_berths junction + drop berth_id

Phase 2b of the berth-recommender refactor (plan §3.4). Every caller of
the legacy `interests.berth_id` column now reads / writes through the
`interest_berths` junction via the helper service introduced in Phase 2a;
the column itself is dropped in a final migration.

Service-layer changes
- interests.service: filter `?berthId=X` becomes EXISTS-against-junction;
  list enrichment uses `getPrimaryBerthsForInterests`; create/update/
  linkBerth/unlinkBerth all dispatch through the junction helpers, with
  createInterest's row insert + junction write sharing a single transaction.
- clients / dashboard / report-generators / search: leftJoin chains pivot
  through `interest_berths` filtered by `is_primary=true`.
- eoi-context / document-templates / berth-rules-engine / portal /
  record-export / queue worker: read primary via `getPrimaryBerth(...)`.
- interest-scoring: berthLinked is now derived from any junction row count.
- dedup/migration-apply + public interest route: write a primary junction
  row alongside the interest insert when a berth is provided.

API contract preserved: list/detail responses still emit `berthId` and
`berthMooringNumber`, derived from the primary junction row, so frontend
consumers (interest-form, interest-detail-header) need no changes.

Schema + migration
- Drop `interestsRelations.berth` and `idx_interests_berth`.
- Replace `berthsRelations.interests` with `interestBerths`.
- Migration 0029_puzzling_romulus drops `interests.berth_id` + the index.
- Tests that previously inserted `interests.berthId` now seed a primary
  junction row alongside the interest.

Verified: vitest 995 passing (1 unrelated pre-existing flake in
maintenance-cleanup.test.ts), tsc clean.

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

tests/integration/dedup/client-merge.test.ts

@@ -11,7 +11,7 @@ import { eq } from 'drizzle-orm';
 
 import { db } from '@/lib/db';
 import { clients, clientContacts, clientNotes, clientMergeLog } from '@/lib/db/schema/clients';
-import { interests } from '@/lib/db/schema/interests';
+import { interests, interestBerths } from '@/lib/db/schema/interests';
 import { mergeClients } from '@/lib/services/client-merge.service';
 import { makeClient, makePort, makeBerth } from '../../helpers/factories';
 
@@ -40,12 +40,20 @@ describe('mergeClients', () => {
       content: 'Loser-side note',
     });
     const berth = await makeBerth({ portId: port.id });
-    await db.insert(interests).values({
-      portId: port.id,
-      clientId: loser.id,
+    const [legacyInterest] = await db
+      .insert(interests)
+      .values({
+        portId: port.id,
+        clientId: loser.id,
+        pipelineStage: 'open',
+        leadCategory: 'general_interest',
+      })
+      .returning();
+    await db.insert(interestBerths).values({
+      interestId: legacyInterest!.id,
       berthId: berth.id,
-      pipelineStage: 'open',
-      leadCategory: 'general_interest',
+      isPrimary: true,
+      isSpecificInterest: true,
     });
 
     // ── Merge ─────────────────────────────────────────────────────────────