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>

internal/storage/sqlite/lazy_init_test.go

@@ -9,6 +9,8 @@ import (
 	"github.com/steveyegge/beads/internal/types"
 )
 
+const testIssueCustom1 = "custom-1"
+
 // TestLazyCounterInitialization verifies that counters are initialized lazily
 // on first use, not by scanning the entire database on every CreateIssue
 func TestLazyCounterInitialization(t *testing.T) {
@@ -163,7 +165,7 @@ func TestLazyCounterInitializationMultiplePrefix(t *testing.T) {
 		t.Fatalf("CreateIssue failed: %v", err)
 	}
 
-	if customIssue.ID != "custom-1" {
+	if customIssue.ID != testIssueCustom1 {
 		t.Errorf("Expected custom-1, got %s", customIssue.ID)
 	}