fix(export): treat any engagement as exported

[malek10xdev]

The exported side of the export split only matched EXPORT rows, so a contact that already had another engagement row landed in the unit count again.

• Add getActivatedContacts: a contact counts as exported as soon as it has any engagement row. EXISTS keeps it at one row per contact even with several engagement rows.
• Redefine the non-exported queries as contacts with no engagement row at all (dropped the type predicate, kept the LEFT JOIN + IS NULL).
• verifyCredits reads the activated set instead of the exported one. The two sets stay a partition of the selection, so the file, the response fields and the 402/266 gates are unchanged.
• SELECT_EXPORTED_CONTACTS / getExportedContacts are untouched; they no longer have a caller, left for a separate cleanup.

Tests

• contacts-export-split.test.ts: only contacts with no engagement row count as units; every selected contact reaches the file; the whole file is handed to registerExportedContacts so an activated contact still gets an EXPORT row; when units run out, activated contacts are kept and the rest trimmed.
• pg-contacts.test.ts: pins the new SQL (EXISTS, no type filter, scoping, ids variant) and the redefined non-exported SQL, plus a guard that the exported lookup still filters on EXPORT.

Checked against the local DB with a 16-contact user (3 exported, 3 enriched including one with a duplicate engagement row, rest untouched): activated 6, not activated 10, and the two sets sum to 16 with no overlap.

[github-actions]

Coverage Report

✅ Passed

Commit: e244141

Summary

	Name	Stmts	Branch	Funcs	Lines
🟡	Total	48.7%	47.4%	54.5%	49%

All files

	Name	Stmts	Branch	Funcs	Lines
🟡	backend/src/controllers/contacts.controller.ts	63.4%	48.3%	77.8%	64.3%
🔴	backend/src/db/pg/PgContacts.ts	40.4%	13.3%	51.7%	39.2%

No coverage changes

	Name	Stmts	Branch	Funcs	Lines
🟡	backend/src/controllers/contacts.controller.ts	63.4%	48.3%	77.8%	64.3%
🔴	backend/src/db/pg/PgContacts.ts	40.4%	13.3%	51.7%	39.2%

Generated by Test Coverage Reporter for commit e244141