Add filter feedback during data export

[joshsmithxrm]

Problem

Users have no visibility into whether filters are being applied during data export. This can lead to unexpected behavior when filters are silently ignored (see #500).

Real-World Impact

With Filter	Without Filter
269,315 records (2:43)	4,962,562 records (7:09)

An 18x difference in exported records with zero feedback about filter status.

Suggested Enhancement

Log when filters are applied:

Exporting customeraddress (filter: country='US' AND et_legacysiebelrowid IS NOT NULL)...

Or at minimum, show filter status in progress output:

Exporting customeraddress... (filtered)
Exporting customeraddress... (no filter)

Bonus: Warn on Empty Filter

If an entity has a <filter> element in the schema but FetchXmlFilter is empty after parsing, warn the user that the filter may be malformed.

Files

• src/PPDS.Migration/Export/ParallelExporter.cs