Allow collecting data from EUNE, NA, KR on top of EUW

- match_collector: query API and build collections for each platform
- match_collector: aggregate champion stats of each platform in one collection with platform annotations
- frontend: replace stats to count matches in platform-specific collections
- frontend: replace "EUW Challengers" with all supported platforms
- dev: adapted scripts to count match in platforms

frontend/server/utils/mongo.ts

@@ -1,5 +1,9 @@
 import { MongoClient } from 'mongodb'
 
+// Available platforms for region-specific match data
+const PLATFORMS = ['EUW1', 'EUN1', 'NA1', 'KR'] as const
+type Platform = (typeof PLATFORMS)[number]
+
 async function connectToDatabase() {
   // Create a MongoClient with a MongoClientOptions object to set the Stable API version
   let uri = `mongodb://${process.env.MONGO_USER}:${process.env.MONGO_PASS}@${process.env.MONGO_HOST}`
@@ -22,4 +26,25 @@ async function fetchLatestPatch(client: MongoClient) {
   return latestPatch!.patch as string
 }
 
-export { connectToDatabase, fetchLatestPatch }
+/**
+ * Get available platforms for a given patch by checking which match collections exist
+ * Note: Match collections are platform-specific (e.g., "15.1_EUW1")
+ * Champion collections are aggregated across all platforms (e.g., "15.1")
+ */
+async function getAvailablePlatforms(client: MongoClient, patch: string): Promise<Platform[]> {
+  const matchesDb = client.db('matches')
+  const collections = await matchesDb.listCollections().toArray()
+  const collectionNames = collections.map(c => c.name)
+
+  const availablePlatforms: Platform[] = []
+  for (const platform of PLATFORMS) {
+    if (collectionNames.includes(`${patch}_${platform}`)) {
+      availablePlatforms.push(platform)
+    }
+  }
+
+  return availablePlatforms
+}
+
+export { connectToDatabase, fetchLatestPatch, getAvailablePlatforms, PLATFORMS }
+export type { Platform }