Add audit start and end dates to audits

ISO audits often span a window distinct from certificate validity.
Store optional audit_start_date and audit_end_date on the audit
record and expose them through GraphQL, MCP, CLI, n8n, and console.

Signed-off-by: Cursor Agent <cursoragent@cursor.com>

Co-authored-by: Bryan FRIMIN <bryan@frimin.fr>

pkg/coredata/migrations/20260728T142906Z.sql

@@ -0,0 +1,22 @@
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+-- SOFTWARE.
+
+ALTER TABLE audits ADD COLUMN audit_start_date DATE;
+ALTER TABLE audits ADD COLUMN audit_end_date DATE;