T21: Collapse 18 migrations to one baseline

[thedancingdeveloper]

Fresh deploy, no upgrade path to preserve.

Acceptance: single 001_baseline.sql; a fresh container reaches /health from an empty database.

[thedancingdeveloper]

🤖 Vogt validation pass — 2026-08-20 (automated review vs dd26a0aa)

Valid and pending. origin/main still carries the full 18-file migration chain (migrations/001_initial.sql through 018_import_candidates.sql); there is no single migrations/001_baseline.sql on the default branch. The collapsed baseline exists only on the unmerged feat/mariadb-baseline branch (PR #107) and is gated behind T20 (#58) sign-off, so the acceptance criterion — a single 001_baseline.sql that a fresh container reaches /health from — is not yet satisfied on main. Leaving open.