Update code references and tests: Bookmann → Bookhoard

Code changes:
- main.go: Update cache directory path
- sidecar.go: Update file extension (.bookmann.json → .bookhoard.json)
- security.go: Update CORS example URLs
- queue_test.go: Update test database name
- feed_test.go: Update test assertions
- phase1_integration_test.go: Update test email addresses
- TEST_COVERAGE.md: Update project references

Part of project rename to Bookhoard.

internal/middleware/security.go

@@ -87,8 +87,8 @@ type CORSSecurityConfig struct {
 func NewSecureCORSConfig() CORSSecurityConfig {
 	return CORSSecurityConfig{
 		AllowedOrigins: []string{
-			"https://bookmann.example.com",
-			"https://*.bookmann.example.com",
+			"https://bookhoard.example.com",
+			"https://*.bookhoard.example.com",
 		},
 		AllowedMethods: []string{"GET", "POST", "PUT", "PATCH", "DELETE", "OPTIONS"},
 		AllowedHeaders: []string{