Fix a real UTC-vs-local timezone mismatch in open-data station timestamps

Found while wiring up real FTP credentials: the open-data portal's
DATETIME field is UTC, but was being stored into weather.dateTime
as-is with no conversion — while the private FTP feed's "Laiks"
column is already Latvia local time and also stored as-is. Both
paths write the same column, so the table has been silently holding
two timelines 2-3h apart since open-data went live, invisible only
because FTP was never actually running with real data until today.
Verified live: at real local time 20:31 EEST, the fix now correctly
produces dateTime=20:00 instead of 17:00, matching what FTP writes
for the same real hour.

src/main/scala/fetch/lvgmc/OpenDataStationService.scala

@@ -11,7 +11,7 @@ import org.typelevel.log4cats.Logger
 import org.typelevel.log4cats.slf4j.Slf4jLogger
 import parse.csv.{WeatherData, WeatherStationData}
 
-import java.time.LocalDateTime
+import java.time.{LocalDateTime, ZoneId, ZoneOffset}
 import scala.util.Try
 
 object OpenDataStationService {
@@ -27,6 +27,14 @@ object OpenDataStationService {
 final class OpenDataStationService private (logger: Logger[IO]) {
   private val pageSize = 5000
 
+  // The open-data portal's DATETIME field is UTC (verified live against real
+  // clock time 2026-08-23); the private FTP feed's "Laiks" column is already
+  // Latvia local time with no conversion needed. Both write into the same
+  // weather.dateTime column, so this path converts to match — otherwise the
+  // two sources silently occupy two different, 2-3h-offset timelines in the
+  // same table instead of one.
+  private val rigaZone = ZoneId.of("Europe/Riga")
+
   private val observationsUrl = sys.env.getOrElse(
     "LVGMC_OPENDATA_OBSERVATIONS_URL",
     "https://data.gov.lv/dati/api/3/action/datastore_search?resource_id=17460efb-ae99-4d1d-8144-1068f184b05f"
@@ -113,7 +121,7 @@ final class OpenDataStationService private (logger: Logger[IO]) {
         city <- stationCities.get(stationId)
         abbreviation <- cursor.downField("ABBREVIATION").as[String].toOption
         datetimeStr <- cursor.downField("DATETIME").as[String].toOption
-        timestamp <- Try(LocalDateTime.parse(datetimeStr)).toOption
+        timestamp <- Try(LocalDateTime.parse(datetimeStr).atZone(ZoneOffset.UTC).withZoneSameInstant(rigaZone).toLocalDateTime).toOption
         value <- cursor.downField("VALUE").as[Double].toOption
       } yield ObservationCell(city, timestamp, abbreviation, value)
     }