📅 Filter employment history by freshness on GET /employments

• New optional updated_at_from and updated_at_to query params on GET /employments — return only employment records updated within a given range (open-ended bounds supported).
• New updated_at timestamp on every employment row, so you can see how fresh each individual record is.

⚙️ What Changes

updated_at range filtering on GET /employments

• GET /employments now accepts optional updated_at_from and updated_at_to query params (format YYYY-MM-DD, e.g. ?updated_at_from=2026-01-01&updated_at_to=2026-03-31). Bounds are inclusive (>= / <=) and a single open-ended bound is supported.
• Each employment row now carries its own updated_at (full ISO-8601) reflecting the real recovery date of that record — distinct from the identifier-level updated_at. Use the per-row value to gauge how fresh each employment record is.
• from > to returns a 400 invalid_input_data error; equal bounds are allowed.

🛠️ No Action Required

These are additive, non-breaking changes. The new query params are optional and the new per-row field appears automatically — existing integrations continue to work as before.