fix(settings): strip env-supplied ApiKeys from the request before persisting (#9438)

GET /api/settings returns settings.ApiKeys as the merged env+runtime list
via ApplicationConfig.ToRuntimeSettings(). The WebUI displays that list and
round-trips it back on POST /api/settings unchanged.

UpdateSettingsEndpoint was then doing:

    appConfig.ApiKeys = append(envKeys, runtimeKeys...)

where runtimeKeys already contained envKeys (because the UI got them from
the merged GET). Every save therefore duplicated the env keys on top of
the previous merge, and also wrote the duplicates to runtime_settings.json
so the duplication survived restarts and compounded with each save. This
is the user-visible behaviour in #9071: the Web UI shows the keys
twice / three times after consecutive saves.

Before we marshal the settings to disk or call ApplyRuntimeSettings, drop
any incoming key that already appears in startupConfig.ApiKeys. The file
on disk now stores only the genuinely runtime-added keys; the subsequent
append(envKeys, runtimeKeys...) produces one copy of each env key, as
intended. Behaviour is unchanged for users who never had env keys set.

Fixes #9071

Co-authored-by: SAY-5 <SAY-5@users.noreply.github.com>

Author: SAY-5

core/http/endpoints/localai/settings.go

@@ -110,6 +110,27 @@ func UpdateSettingsEndpoint(app *application.Application) echo.HandlerFunc {
 			})
 		}
 
+		// The UI reads ApiKeys from GET /api/settings, which already returns the
+		// merged env+runtime list. When the user clicks Save, the same merged
+		// list comes back in the POST body. Strip the env-supplied keys from
+		// the incoming list before we persist or re-merge, otherwise each save
+		// duplicates the env keys on top of the previous merge (#9071).
+		if settings.ApiKeys != nil {
+			envKeys := startupConfig.ApiKeys
+			envSet := make(map[string]struct{}, len(envKeys))
+			for _, k := range envKeys {
+				envSet[k] = struct{}{}
+			}
+			runtimeOnly := make([]string, 0, len(*settings.ApiKeys))
+			for _, k := range *settings.ApiKeys {
+				if _, fromEnv := envSet[k]; fromEnv {
+					continue
+				}
+				runtimeOnly = append(runtimeOnly, k)
+			}
+			settings.ApiKeys = &runtimeOnly
+		}
+
 		settingsFile := filepath.Join(appConfig.DynamicConfigsDir, "runtime_settings.json")
 		settingsJSON, err := json.MarshalIndent(settings, "", "  ")
 		if err != nil {