feat: add Prisma schema for pairing history

Add MongoDB schema with Prisma 6.8.2 for tracking:
- ServerEvent: events per server (coffee chats, study groups, etc.)
- UserPairingHistory: user pairing records per server
- PairingRecord: individual pairing entries with event context

This enables smart grouping that avoids recent pairings per-event.

package.json

@@ -1,5 +1,12 @@
 {
   "name": "rondelle",
+  "pnpm": {
+    "onlyBuiltDependencies": [
+      "@prisma/engines",
+      "esbuild",
+      "prisma"
+    ]
+  },
   "version": "0.0.0",
   "description": "",
   "main": "./prod/index.js",
@@ -17,6 +24,12 @@
     "@nhcarrigan/eslint-config": "5.2.0",
     "@nhcarrigan/typescript-config": "1.0.0",
     "@types/node": "22.10.6",
+    "prisma": "6.8.2",
     "typescript": "5.7.3"
+  },
+  "dependencies": {
+    "@nhcarrigan/logger": "1.1.1",
+    "@prisma/client": "6.8.2",
+    "discord.js": "14.25.1"
   }
 }

prisma/schema.prisma

@@ -0,0 +1,35 @@
+generator client {
+    provider = "prisma-client-js"
+}
+
+datasource db {
+    provider = "mongodb"
+    url      = env("MONGO_URI")
+}
+
+model ServerEvent {
+    id        String   @id @default(auto()) @map("_id") @db.ObjectId
+    serverId  String
+    eventId   String
+    eventName String
+    createdAt DateTime @default(now())
+    createdBy String
+
+    @@unique([serverId, eventId])
+    @@index([serverId])
+}
+
+model UserPairingHistory {
+    id       String          @id @default(auto()) @map("_id") @db.ObjectId
+    userId   String
+    serverId String
+    pairings PairingRecord[]
+
+    @@unique([userId, serverId])
+}
+
+type PairingRecord {
+    recipientId String
+    eventId     String
+    sessionDate DateTime
+}