feat: add geolocation fields to session and implement geo stats endpoint

- Added country, city, countryCode, latitude, and longitude fields to the Session model.
- Updated geoip service to fetch and store geolocation data based on user IP.
- Created a new admin endpoint to retrieve geolocation statistics, including user counts by country and city.
- Enhanced admin page to display geolocation statistics with expandable city details.
- Introduced caching for geolocation data to optimize performance.

apps/backend/prisma/auth.prisma

@@ -20,15 +20,20 @@ model User {
 }
 
 model Session {
-    id        String   @id
-    expiresAt DateTime
-    token     String
-    createdAt DateTime @default(now())
-    updatedAt DateTime @updatedAt
-    ipAddress String?
-    userAgent String?
-    userId    String
-    user      User     @relation(fields: [userId], references: [id], onDelete: Cascade)
+    id          String    @id
+    expiresAt   DateTime
+    token       String
+    createdAt   DateTime  @default(now())
+    updatedAt   DateTime  @updatedAt
+    ipAddress   String?
+    userAgent   String?
+    country     String?
+    city        String?
+    countryCode String?
+    latitude    Float?
+    longitude   Float?
+    userId      String
+    user        User      @relation(fields: [userId], references: [id], onDelete: Cascade)
 
     @@unique([token])
     @@index([userId])

apps/backend/prisma/migrations/20260610131124_add_session_geo_fields/migration.sql

@@ -0,0 +1,6 @@
+-- AlterTable
+ALTER TABLE "sessions" ADD COLUMN     "city" TEXT,
+ADD COLUMN     "country" TEXT,
+ADD COLUMN     "countryCode" TEXT,
+ADD COLUMN     "latitude" DOUBLE PRECISION,
+ADD COLUMN     "longitude" DOUBLE PRECISION;