test(16-02): verify new Device fields in integration test

- Assert DeviceType defaults to "routeros" via COALESCE
- Assert SNMPPort defaults to 161 via COALESCE
- Assert SNMPVersion, SNMPProfileID, CredentialProfileID are nil for
  existing RouterOS devices without profile links
- Assert ProfileEncryptedCredentials and ProfileEncryptedCredentialsTransit
  are nil when no credential profile is linked
- Update test schema with device_type, snmp_port, snmp_version,
  snmp_profile_id, credential_profile_id columns
- Add credential_profiles table to test schema for LEFT JOIN

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

poller/internal/store/devices_integration_test.go

@@ -87,6 +87,15 @@ func TestDeviceStore_FetchDevices_Integration(t *testing.T) {
 			assert.Equal(t, "7.16", *d.RouterOSVersion)
 			require.NotNil(t, d.MajorVersion)
 			assert.Equal(t, 7, *d.MajorVersion)
+
+			// New fields: verify COALESCE defaults for existing RouterOS devices.
+			assert.Equal(t, "routeros", d.DeviceType, "COALESCE should default to routeros")
+			assert.Equal(t, 161, d.SNMPPort, "COALESCE should default to 161")
+			assert.Nil(t, d.SNMPVersion, "SNMPVersion should be nil for RouterOS devices")
+			assert.Nil(t, d.SNMPProfileID, "SNMPProfileID should be nil for RouterOS devices")
+			assert.Nil(t, d.CredentialProfileID, "CredentialProfileID should be nil when not linked")
+			assert.Nil(t, d.ProfileEncryptedCredentials, "ProfileEncryptedCredentials should be nil when no profile linked")
+			assert.Nil(t, d.ProfileEncryptedCredentialsTransit, "ProfileEncryptedCredentialsTransit should be nil when no profile linked")
 		}
 	}
 }