chore: create migration file to deprecate announcements collection

migrations/20260806000000-deprecate-announcements.mjs

@@ -0,0 +1,34 @@
+export const up = async (db) => {
+  await db.collection('announcements').drop();
+};
+
+export const down = async (db) => {
+  await db.createCollection('announcements', {
+    validator: {
+      $jsonSchema: {
+        bsonType: 'object',
+        title: 'Announcements Object Validation',
+        required: ['title', 'description', 'time'],
+        properties: {
+          _id: {
+            bsonType: 'objectId',
+            description: '_id must be an ObjectId',
+          },
+          title: {
+            bsonType: 'string',
+            description: 'title must be a string',
+          },
+          description: {
+            bsonType: 'string',
+            description: 'description must be a string',
+          },
+          time: {
+            bsonType: 'date',
+            description: 'time must be a date.',
+          },
+        },
+        additionalProperties: false,
+      },
+    },
+  });
+};