Channel Store: No SELECT * (#32167)

* Replace SELECT * with explicit column lists in channel store

Migrates channel_store.go away from SELECT * patterns to explicit column
lists for better performance, maintainability, and schema safety.

- Replace GetPinnedPosts raw SQL with query builder using postSliceColumns()
- Replace "cc.*" in group channel search with channelSliceColumns()
- Replace GetChannelsBatchForIndexing raw SQL with query builder
- Replace channel member and team queries with respective column helpers
- Use SelectBuilder helper instead of manual ToSql() calls

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

* Replace SELECT * with COUNT(*) in user_test.go

Replaces unnecessary SELECT * queries with SELECT COUNT(*) in
TestPermanentDeleteUser bot count verification. Only needs to check
the count of bots, not retrieve full bot records.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

---------

Co-authored-by: Claude <noreply@anthropic.com>

server/channels/app/user_test.go

@@ -1248,12 +1248,12 @@ func TestPermanentDeleteUser(t *testing.T) {
 	})
 	assert.Nil(t, err)
 
-	bots1 := []*model.Bot{}
-	bots2 := []*model.Bot{}
+	var botCount1 int
+	var botCount2 int
 
-	err1 := th.SQLStore.GetMaster().Select(&bots1, "SELECT * FROM Bots")
+	err1 := th.SQLStore.GetMaster().Get(&botCount1, "SELECT COUNT(*) FROM Bots")
 	assert.NoError(t, err1)
-	assert.Equal(t, 1, len(bots1))
+	assert.Equal(t, 1, botCount1)
 
 	// test that bot is deleted from bots table
 	retUser1, err := th.App.GetUser(bot.UserId)
@@ -1262,9 +1262,9 @@ func TestPermanentDeleteUser(t *testing.T) {
 	err = th.App.PermanentDeleteUser(th.Context, retUser1)
 	assert.Nil(t, err)
 
-	err1 = th.SQLStore.GetMaster().Select(&bots2, "SELECT * FROM Bots")
+	err1 = th.SQLStore.GetMaster().Get(&botCount2, "SELECT COUNT(*) FROM Bots")
 	assert.NoError(t, err1)
-	assert.Equal(t, 0, len(bots2))
+	assert.Equal(t, 0, botCount2)
 
 	scheduledPost1 := &model.ScheduledPost{
 		Draft: model.Draft{