## Summary
Fix bug where `AllAndCount(true)` with multiple fields generates invalid
SQL `COUNT(field1, field2, ...)` causing syntax error.
## Root Cause
When `useFieldForCount=true`, the COUNT query inherits the fields
configuration from the model:
```go
// Before (buggy code)
if !useFieldForCount {
countModel.fields = []any{Raw("1")}
}
// When useFieldForCount=true, fields remain as ["id", "nickname"]
// Generates: SELECT COUNT(id, nickname) FROM table ❌
```
## Fix
Always use `COUNT(1)` regardless of `useFieldForCount` parameter since
COUNT() accepts only one argument:
```go
// After (fixed code)
// Always use COUNT(1) for counting, regardless of useFieldForCount.
// COUNT() accepts only one argument, so we can't use multiple fields.
countModel.fields = []any{Raw("1")}
```
Applied to both `AllAndCount()` and `ScanAndCount()` methods.
## Tests
Added `Test_Issue4698` with 5 test cases:
1. AllAndCount(true) with multiple fields
2. AllAndCount(false) with multiple fields (baseline)
3. ScanAndCount with multiple fields
4. AllAndCount with single field
5. AllAndCount with WHERE condition
All tests verify that COUNT generates valid SQL and returns correct
count.
## Related
Fixes#4698
Ref #4703 (discovered during pagination test development)
612e545ae2