feat: add Activity type system, DB migration, and self-only showActivity in sanitizeUser

- Add Activity, ActivityType, ActivityTimestamps, ActivityAssets types to shared types
- Add activity_update client event and activities field on presence_update server event
- Add userActivities to ready payload and showActivity to User/UpdateUserRequest
- Create shared activities.ts with ACTIVITY_LIMITS, ACTIVITY_PRIORITY, getPrimaryActivity
- Add show_activity column to users table (schema + migration)
- Update sanitizeUser with isSelf parameter; only include showActivity for self
- Fix .map(sanitizeUser) calls to use arrow wrapper to prevent index-as-boolean bug
- Mark auth routes (register/login) as isSelf=true since they return own user data

packages/server/src/ws/handler.ts

@@ -682,7 +682,7 @@ function buildReadyPayload(userId: string): {
   if (!userRow) {
     throw new Error('User not found');
   }
-  const user = sanitizeUser(userRow);
+  const user = sanitizeUser(userRow, true);
 
   // Get user's space memberships
   const memberships = db.select()
@@ -931,7 +931,7 @@ function buildReadyPayload(userId: string): {
       const members = memberRows
         .map(m => dmUserMap.get(m.userId))
         .filter((u): u is NonNullable<typeof u> => u != null)
-        .map(sanitizeUser);
+        .map(u => sanitizeUser(u));
 
       const last = dmLastMsgMap.get(dm.dmChannelId) ?? null;