Enhance environment variable documentation and configuration

- Updated `.env.example` to include new environment variables for server access logging and security settings, ensuring comprehensive configuration options.
- Revised `docker-entrypoint.sh` to clarify the source of supported environment variables.
- Improved `README.md` to reflect the latest environment variable changes and maintain synchronization with the canonical list in `internal/config/config.go`.
- Added tests to ensure documentation consistency across `.env.example` and `README.md`, preventing future discrepancies.

internal/http/handlers_integration_helpers_test.go

@@ -18,6 +18,7 @@ type testServerOptions struct {
 	maxUploadBytes  int64
 	defaultTTL      time.Duration
 	rateLimitEnable bool
+	rawCacheBytes   int64 // 0 => default 64MiB
 }
 
 func newTestHandler(t *testing.T, opts testServerOptions) http.Handler {
@@ -36,6 +37,11 @@ func newTestHandlerAndStore(t *testing.T, opts testServerOptions) (http.Handler,
 		t.Fatalf("NewFilesystemStore() error = %v", err)
 	}
 
+	rawCacheBytes := opts.rawCacheBytes
+	if rawCacheBytes <= 0 {
+		rawCacheBytes = 64 * 1024 * 1024
+	}
+
 	cfg := config.Config{
 		Server: config.ServerConfig{
 			ListenAddr: ":0",
@@ -43,7 +49,7 @@ func newTestHandlerAndStore(t *testing.T, opts testServerOptions) (http.Handler,
 		Limits: config.LimitsConfig{
 			MaxUploadSizeBytes: opts.maxUploadBytes,
 			DefaultTTLDuration: opts.defaultTTL,
-			RawCacheMaxBytes:   64 * 1024 * 1024,
+			RawCacheMaxBytes:   rawCacheBytes,
 			RawCacheMaxEntries: 32,
 		},
 		Storage: config.StorageConfig{