fix: brand registry house/sub-brand counts

[bokelley]

Summary

Supersedes #1132. The brand registry page shows house/sub-brand counts but they were always zero because:

• The getAllBrandsForRegistry query hardcoded NULL as keller_type for hosted brands, so they were never counted
• The API response was missing houses, sub_brands, and with_manifest stats that the frontend expected
• Seeded discovered brands had no keller_type set

Fixes:

• LEFT JOIN hosted_brands to discovered_brands to pull actual keller_type, defaulting to master for self-hosted brands with no discovered record
• Add houses, sub_brands, with_manifest stats to the registry API response
• Backfill migration for seeded brands with idempotency guards (WHERE keller_type IS NULL) to avoid overwriting enrichment/community edits
• Fix data conflicts from Fix a brand and sub brand count on brand registry page #1132: removed Pfizer from independent list (it's a master), removed duplicate Lilly entry, removed NBCUniversal from master list (it's a Comcast sub-brand)

Test plan

• All 323 unit tests pass
• TypeScript typecheck clean
• OpenAPI spec unchanged
• Migration applies cleanly in Docker (verified: 40 master, 38 independent, 65 sub_brand)
• Verified query returns correct stats via direct DB query (195 total, 79 houses, 65 sub-brands)
• No duplicate rows from LEFT JOIN (verified with hosted brand data)

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