feat: Gezeiten über BSH-OGC-API mit Stations-Suche

Amtliche BSH-Wasserstandsvorhersage ersetzt Open-Meteo als Primärquelle;
nächster Pegel per Haversine, Open-Meteo nur außerhalb 75 km Reichweite.

Co-authored-by: Cursor <cursoragent@cursor.com>

server/src/utils/tideProvider.ts

@@ -0,0 +1,58 @@
+import { fetchBshTidesForCoordinates, MAX_BSH_DISTANCE_KM } from './bshTides.js'
+import {
+  fetchTidesForCoordinates as fetchOpenMeteoTidesForCoordinates,
+  fetchTidesForPlace as fetchOpenMeteoTidesForPlace,
+  geocodePlace,
+  type TideLookupResult
+} from './openMeteoTides.js'
+
+export type TideProviderResult = TideLookupResult & {
+  distanceKm?: number
+  fallback?: 'open_meteo'
+}
+
+export async function fetchTidesForCoordinates(
+  lat: number,
+  lon: number,
+  options?: { name?: string; source?: 'coordinates' | 'geocoded' }
+): Promise<TideProviderResult> {
+  try {
+    const bsh = await fetchBshTidesForCoordinates(lat, lon)
+    return bsh
+  } catch (error: unknown) {
+    const message = error instanceof Error ? error.message : ''
+    const tooFar = message === 'bsh_station_too_far'
+    const noStation = message === 'no_bsh_station' || message === 'bsh_empty_station_list'
+    const noData = message === 'no_tide_data'
+
+    if (!tooFar && !noStation && !noData) {
+      console.warn('BSH tide lookup failed, trying Open-Meteo fallback:', error)
+    }
+
+    const fallback = await fetchOpenMeteoTidesForCoordinates(lat, lon, options)
+    return {
+      ...fallback,
+      fallback: 'open_meteo',
+      tides: {
+        data: {
+          ...fallback.tides.data,
+          source: `${fallback.tides.data.source} (Fallback — keine BSH-Station innerhalb ${MAX_BSH_DISTANCE_KM} km)`
+        }
+      }
+    }
+  }
+}
+
+export async function fetchTidesForPlace(query: string): Promise<TideProviderResult> {
+  const place = await geocodePlace(query)
+  if (!place) {
+    const err = new Error('place_not_found') as Error & { status?: number }
+    err.status = 404
+    throw err
+  }
+
+  return fetchTidesForCoordinates(place.latitude, place.longitude, {
+    name: place.name,
+    source: 'geocoded'
+  })
+}