fix: Validate edits to env (config)

src/web/backend/settings/handlers.go

@@ -68,6 +68,10 @@ func (s *Settings) HandleSaveConfig(w http.ResponseWriter, r *http.Request) {
 		http.Error(w, err.Error(), http.StatusBadRequest)
 		return
 	}
+	if err := validateEnvText(string(data)); err != nil {
+		http.Error(w, "invalid .env content: "+err.Error(), http.StatusBadRequest)
+		return
+	}
 	if err := os.WriteFile(s.cfg.WebEnvPath, data, 0600); err != nil {
 		http.Error(w, err.Error(), http.StatusInternalServerError)
 		return

src/web/backend/settings/settings.go

@@ -1,9 +1,9 @@
 package settings
 
 import (
-	"strings"
-	"os"
 	"fmt"
+	"os"
+	"strings"
 
 	"explo/src/web/backend/app"
 )
@@ -21,6 +21,7 @@ type Settings struct {
 func NewSettings(Config app.Config) *Settings {
 	return &Settings{cfg: Config}
 }
+
 // parseEnvText parses key=value lines, ignoring comments, blanks and unquotes variables
 func (s *Settings) ParseEnvText(text string) map[string]string {
 	out := map[string]string{}
@@ -49,6 +50,24 @@ func (s *Settings) ParseEnvText(text string) map[string]string {
 	return out
 }
 
+// validateEnvText rejects content that isn't valid .env syntax before it's written to
+// disk. cleanenv.ReadConfig fails hard on any non-blank, non-comment line without a "=",
+// which causes a crash loop for the container with no way tofix since the UI becomes
+// inaccessible.Mirrors ParseEnvText's line rules,but treats a missing "=" as an error
+// instead of silently skipping the line.
+func validateEnvText(text string) error {
+	for i, line := range strings.Split(text, "\n") {
+		t := strings.TrimSpace(line)
+		if t == "" || strings.HasPrefix(t, "#") {
+			continue
+		}
+		if !strings.Contains(t, "=") {
+			return fmt.Errorf("line %d is not valid .env syntax (expected KEY=value): %q", i+1, t)
+		}
+	}
+	return nil
+}
+
 // updateEnvKeys reads the env file (falling back to fallback if missing), updates the
 // given key=value pairs in-place preserving comments, and writes the result back.
 func (s *Settings) UpdateEnvKeys(updates map[string]string, fallback []byte) error {
@@ -119,4 +138,4 @@ func formatEnvValue(v string) string {
 	}
 
 	return v
-}
+}