data: migrate stored model_keys for earbuds and Watch Ultra 3 to normalizer keys #1123

Split from #1113 (PR #1121), which fixes the normalizer side. The data side needs a DOS-Me migration that is not applied yet.

Scope

Stored model_key values that the normalizer no longer produces:

• samsung:galaxy-buds3-pro:64gb -> samsung:galaxy-buds3-pro:unknown (earbuds have no storage, rules ProductNormalizer: earbuds keyed :1gb, iPad RAM taken as storage, AirPods Pro by year #643/ProductNormalizer: benchmark and phone-template specs override the title (RAM, earbud storage, SAR, Face ID) #657)
• apple:airpods-pro-3:standard -> apple:airpods-pro-3:unknown
• apple:watch-ultra-3-49mm:64gb -> apple:watch-ultra-3:64gb (single-size line, no size in key)

The proposal (idempotent, skips a row when the target key already exists) and the matching seed diff for flagship-seed-data.ts are in #1113 (comment)

Ordering constraint

jobs/backfill-specs.ts --apply looks masters up by the seed key and inserts when none is found. The seed change must ship in the same step as the migration, or backfill creates duplicate masters.

Acceptance

• JOY approves the migration (AGENTS.md 0.1); it is applied through DOS-Me.
• The seed change merges right after, and a read-only check shows no duplicate masters.