Add recon UX backend: scan history, export, and streaming tests.

Persist recon scans in SQLite with history diff and export routes; wire WebSocket streaming test coverage and relay path_tracer_hints in fleet reports.

server/internal/db/sqlite.go

@@ -279,6 +279,9 @@ func (d *Database) migrate() error {
 	if err := d.ensureSeerTables(); err != nil {
 		return fmt.Errorf("seer migration: %w", err)
 	}
+	if err := d.ensureReconScansTable(); err != nil {
+		return fmt.Errorf("recon_scans migration: %w", err)
+	}
 	if err := d.ensureSubnetDiscoveriesTable(); err != nil {
 		return fmt.Errorf("subnet_discoveries migration: %w", err)
 	}