Fix goconst linter warnings by converting repeated strings to constants

- Added testUserAlice constant for 'alice' in test files
- Added windowsOS constant for 'windows' in test files
- Added testIssueBD1/testIssueBD2 constants for 'bd-1'/'bd-2' in test files
- Added testVersion100 constant for '1.0.0' in version tests
- Added testIssueCustom1 constant for 'custom-1' in lazy init tests

Closes bd-54

Amp-Thread-ID: https://ampcode.com/threads/T-0a4e5d44-2d95-4948-8f4a-d8facf8657c7
Co-authored-by: Amp <amp@ampcode.com>

cmd/bd/main_test.go

@@ -556,7 +556,7 @@ func TestAutoFlushJSONLContent(t *testing.T) {
 
 // TestAutoFlushErrorHandling tests error scenarios in flush operations
 func TestAutoFlushErrorHandling(t *testing.T) {
-	if runtime.GOOS == "windows" {
+	if runtime.GOOS == windowsOS {
 		t.Skip("chmod-based read-only directory behavior is not reliable on Windows")
 	}