Add legacy database structural reference for non-Windows machines

docs/LEGACY_DATABASES.md documents all three source Access databases
(every table, column, type, and known data-quality quirk) generated
from a live read of the real files, so no Windows/Access driver is
needed to understand their structure going forward.

New migration/ tooling: catalog_schema.py connects to the real files
and walks every table (including excluded scratch tables);
render_catalog_md.py renders that into the doc's appendix. Raw output
checked in at migration/catalog.json so the doc can be regenerated
without touching Access again.

RESUME.md

@@ -37,6 +37,7 @@ infrastructure decisions below.
 - `C:\Users\ricar\Downloads\Jorge\SEGUROS 16.mdb` — insurance frontend shell, **empty**, all data is in `_be`
 - `C:\Users\ricar\Downloads\Jorge\SEGUROS 16_be.mdb` — insurance backend, 64 tables, ~882MB
 - `C:\Users\ricar\Downloads\Jorge\SCOTHIA.mdb` — office's own Scotiabank checking register ("chequera"), 7 tables, ~3MB
+- **Full structural reference for all three, usable without Windows or the original files:** [`docs/LEGACY_DATABASES.md`](docs/LEGACY_DATABASES.md) — every table, every column with type/nullability, the cross-reference keys between the three databases, and every known data-quality quirk (the UTF-16 decode bug, the corrupted `MULT` row, near-duplicate snapshot tables, etc.), all generated from a live read of the real files via `migration/catalog_schema.py`. Regenerate it if the source files change; the raw JSON it's built from is checked in at `migration/catalog.json`.
 - `C:\Users\ricar\Downloads\jorgecuadros_app.sql` and `jorgecuadros_app (1).sql` — MySQL dumps of the customer-portal's **tracking/analytics** sidecar DB (`browse_tracking`, `devices` push-tokens, `task_tracking`) from `mysql.freakma.com`. **Not** the portal's real data DB — see open item #1 below.
 
 **Old internal app (reference-only, not being built on):**