refactor: rename whitelist package to allowlist, fix stuttering

- Rename internal/whitelist/ → internal/allowlist/
- Rename type HostWhitelist → HostAllowList
- Rename constructor NewHostWhitelist() → New()
- Rename method IsWhitelisted() → IsAllowed()
- Update all imports and references in service.go

No logic changes — purely naming improvements per review feedback.

internal/imgcache/service.go

@@ -11,8 +11,8 @@ import (
 	"time"
 
 	"github.com/dustin/go-humanize"
+	"sneak.berlin/go/pixa/internal/allowlist"
 	"sneak.berlin/go/pixa/internal/imageprocessor"
-	"sneak.berlin/go/pixa/internal/whitelist"
 )
 
 // Service implements the ImageCache interface, orchestrating cache, fetcher, and processor.
@@ -21,7 +21,7 @@ type Service struct {
 	fetcher         Fetcher
 	processor       *imageprocessor.ImageProcessor
 	signer          *Signer
-	whitelist       *whitelist.HostWhitelist
+	allowlist       *allowlist.HostAllowList
 	log             *slog.Logger
 	allowHTTP       bool
 	maxResponseSize int64
@@ -86,7 +86,7 @@ func NewService(cfg *ServiceConfig) (*Service, error) {
 		fetcher:         fetcher,
 		processor:       imageprocessor.New(imageprocessor.Params{MaxInputBytes: maxResponseSize}),
 		signer:          signer,
-		whitelist:       whitelist.NewHostWhitelist(cfg.Whitelist),
+		allowlist:       allowlist.New(cfg.Whitelist),
 		log:             log,
 		allowHTTP:       allowHTTP,
 		maxResponseSize: maxResponseSize,
@@ -382,7 +382,7 @@ func (s *Service) Stats(ctx context.Context) (*CacheStats, error) {
 
 // ValidateRequest validates the request signature if required.
 func (s *Service) ValidateRequest(req *ImageRequest) error {
-	// Check if host is whitelisted (no signature required)
+	// Check if host is allowed (no signature required)
 	sourceURL := req.SourceURL()
 
 	parsedURL, err := url.Parse(sourceURL)
@@ -390,11 +390,11 @@ func (s *Service) ValidateRequest(req *ImageRequest) error {
 		return fmt.Errorf("invalid source URL: %w", err)
 	}
 
-	if s.whitelist.IsWhitelisted(parsedURL) {
+	if s.allowlist.IsAllowed(parsedURL) {
 		return nil
 	}
 
-	// Signature required for non-whitelisted hosts
+	// Signature required for non-allowed hosts
 	return s.signer.Verify(req)
 }