feat(config): support *_MB env vars for upload size limits

- Add `applyMegabytesOrBytesEnv` to accept size settings in either bytes or MB
- Prefer `*_BYTES` when set, otherwise convert `*_MB` to bytes with overflow guard
- Add coverage for MB-based environment overrides
- Introduce `static/js/upload-popups.js` to lazy-load and cache popup templatesfeat(config): support *_MB env vars for upload size limits

- Add `applyMegabytesOrBytesEnv` to accept size settings in either bytes or MB
- Prefer `*_BYTES` when set, otherwise convert `*_MB` to bytes with overflow guard
- Add coverage for MB-based environment overrides
- Introduce `static/js/upload-popups.js` to lazy-load and cache popup templates

lib/config/config.go

@@ -2,6 +2,7 @@ package config
 
 import (
 	"fmt"
+	"math"
 	"os"
 	"path/filepath"
 	"strconv"
@@ -197,10 +198,6 @@ func Load() (*Config, error) {
 	}{
 		{SettingDefaultGuestExpirySecs, "WARPBOX_DEFAULT_GUEST_EXPIRY_SECONDS", 0, &cfg.DefaultGuestExpirySeconds},
 		{SettingMaxGuestExpirySecs, "WARPBOX_MAX_GUEST_EXPIRY_SECONDS", 0, &cfg.MaxGuestExpirySeconds},
-		{SettingGlobalMaxFileSizeBytes, "WARPBOX_GLOBAL_MAX_FILE_SIZE_BYTES", 0, &cfg.GlobalMaxFileSizeBytes},
-		{SettingGlobalMaxBoxSizeBytes, "WARPBOX_GLOBAL_MAX_BOX_SIZE_BYTES", 0, &cfg.GlobalMaxBoxSizeBytes},
-		{SettingDefaultUserMaxFileBytes, "WARPBOX_DEFAULT_USER_MAX_FILE_SIZE_BYTES", 0, &cfg.DefaultUserMaxFileSizeBytes},
-		{SettingDefaultUserMaxBoxBytes, "WARPBOX_DEFAULT_USER_MAX_BOX_SIZE_BYTES", 0, &cfg.DefaultUserMaxBoxSizeBytes},
 		{SettingSessionTTLSeconds, "WARPBOX_SESSION_TTL_SECONDS", 60, &cfg.SessionTTLSeconds},
 	}
 	for _, item := range envInt64s {
@@ -208,6 +205,22 @@ func Load() (*Config, error) {
 			return nil, err
 		}
 	}
+	sizeEnvVars := []struct {
+		key       string
+		mbName    string
+		bytesName string
+		target    *int64
+	}{
+		{SettingGlobalMaxFileSizeBytes, "WARPBOX_GLOBAL_MAX_FILE_SIZE_MB", "WARPBOX_GLOBAL_MAX_FILE_SIZE_BYTES", &cfg.GlobalMaxFileSizeBytes},
+		{SettingGlobalMaxBoxSizeBytes, "WARPBOX_GLOBAL_MAX_BOX_SIZE_MB", "WARPBOX_GLOBAL_MAX_BOX_SIZE_BYTES", &cfg.GlobalMaxBoxSizeBytes},
+		{SettingDefaultUserMaxFileBytes, "WARPBOX_DEFAULT_USER_MAX_FILE_SIZE_MB", "WARPBOX_DEFAULT_USER_MAX_FILE_SIZE_BYTES", &cfg.DefaultUserMaxFileSizeBytes},
+		{SettingDefaultUserMaxBoxBytes, "WARPBOX_DEFAULT_USER_MAX_BOX_SIZE_MB", "WARPBOX_DEFAULT_USER_MAX_BOX_SIZE_BYTES", &cfg.DefaultUserMaxBoxSizeBytes},
+	}
+	for _, item := range sizeEnvVars {
+		if err := cfg.applyMegabytesOrBytesEnv(item.key, item.mbName, item.bytesName, 0, item.target); err != nil {
+			return nil, err
+		}
+	}
 
 	envInts := []struct {
 		key    string
@@ -404,6 +417,34 @@ func (cfg *Config) applyInt64Env(key string, name string, min int64, target *int
 	return nil
 }
 
+func (cfg *Config) applyMegabytesOrBytesEnv(key string, mbName string, bytesName string, min int64, target *int64) error {
+	if rawBytes := strings.TrimSpace(os.Getenv(bytesName)); rawBytes != "" {
+		parsed, err := parseInt64(rawBytes, min)
+		if err != nil {
+			return fmt.Errorf("%s: %w", bytesName, err)
+		}
+		*target = parsed
+		cfg.setValue(key, strconv.FormatInt(parsed, 10), SourceEnv)
+		return nil
+	}
+
+	rawMB := strings.TrimSpace(os.Getenv(mbName))
+	if rawMB == "" {
+		return nil
+	}
+	parsedMB, err := parseInt64(rawMB, min)
+	if err != nil {
+		return fmt.Errorf("%s: %w", mbName, err)
+	}
+	if parsedMB > math.MaxInt64/(1024*1024) {
+		return fmt.Errorf("%s: is too large", mbName)
+	}
+	parsedBytes := parsedMB * 1024 * 1024
+	*target = parsedBytes
+	cfg.setValue(key, strconv.FormatInt(parsedBytes, 10), SourceEnv)
+	return nil
+}
+
 func (cfg *Config) applyIntEnv(key string, name string, min int, target *int) error {
 	raw := strings.TrimSpace(os.Getenv(name))
 	if raw == "" {