fix(parts): dedupe ingest path + clean ~108k duplicate rows

Backfill + reactive prefetch can re-drill the same category multiple
times, and the parts insert path had no dedupe guard. Result: 8.2%
duplicate rows on pl24, 14.5% on parts-catalogs, and 33.7% on emex —
~108k extra rows across 7,571 categories on 224 vehicles. Every drilled
catalog page rendered each part twice (the Tampon example: 32 rows for
19 distinct OEMs).

* Migration 0010 — phase 1 deletes existing dupes preserving the
  oldest row per (vehicle_id, category_id, oem_code, name, position)
  group; phase 2 adds a UNIQUE INDEX over the same tuple with NULLS NOT
  DISTINCT (PG 15+) so null position/vehicle_id collapse like equal
  values rather than each counting as its own "distinct" row. Idempotent
  CREATE UNIQUE INDEX IF NOT EXISTS so the runner is safe to re-apply.
* All five insert(parts).values(...).returning() call sites
  (parts.service, categories.service ×3, catalog.service) get
  .onConflictDoNothing() so future re-drills no-op instead of erroring
  on the new constraint. `.returning()` continues to surface only the
  newly-inserted rows; existing logs read `Stored N parts` as actual
  net insertions, which is what we want.

Dry-run on dev DB: 524,540 → 425,186 parts (99,354 dupes deleted), index
created cleanly. Same delta expected on prod (~108k drop).

drizzle-orm 0.41 doesn't expose .nullsNotDistinct() on the index builder
so the constraint is owned by raw SQL — see the inline comment in the
parts schema and the migration file. Future schema generators should NOT
try to drop or rewrite this index.

apps/api/drizzle/0010_dedupe_parts.sql

@@ -0,0 +1,21 @@
+-- Phase 1: remove existing duplicate rows.
+-- "Duplicate" = same (vehicle_id, category_id, oem_code, name, position).
+-- Backfill + reactive prefetch can re-drill the same category multiple times;
+-- without a unique constraint that re-insert kept all rows, leaving 8–34%
+-- duplicate per source (~108k extra rows of ~588k). Keep the oldest row per
+-- group (preserves original created_at) and drop the rest.
+DELETE FROM "parts" WHERE id IN (
+  SELECT id FROM (
+    SELECT id, row_number() OVER (
+      PARTITION BY vehicle_id, category_id, oem_code, name, position
+      ORDER BY created_at ASC, id ASC
+    ) AS rn FROM "parts"
+  ) t WHERE rn > 1
+);
+--> statement-breakpoint
+
+-- Phase 2: prevent future dupes. NULLS NOT DISTINCT (Postgres 15+) so NULL
+-- position / NULL vehicle_id collapse like equal values rather than each
+-- counting as a separate "distinct" row.
+CREATE UNIQUE INDEX IF NOT EXISTS "parts_dedup_idx" ON "parts"
+  (vehicle_id, category_id, oem_code, name, position) NULLS NOT DISTINCT;

apps/api/drizzle/meta/_journal.json

@@ -71,6 +71,13 @@
       "when": 1779703007129,
       "tag": "0009_referral_rewards_rework",
       "breakpoints": true
+    },
+    {
+      "idx": 10,
+      "version": "7",
+      "when": 1780281600000,
+      "tag": "0010_dedupe_parts",
+      "breakpoints": true
     }
   ]
 }