Make Resend from-address config-only; drop credential status rows

The Settings page no longer renders the Resend From Address input or any
of the read-only "Set in config.toml" credential status rows (Apify key,
eBay id/secret, ntfy auth, Resend key). Those rows looked like editable
inputs but were dead text, and duplicated what the Test buttons verify
more authoritatively.

- resend_from is now sourced only from config.toml ([resend] from); it is
  removed from settingsKeys, the test-Resend handler, the scheduler email
  client, and the schema seed.
- Removed the credStatus templ component, the CredentialStatus field on
  SettingsData, and the credentialStatus() handler helper.

internal/handlers/settings.go

@@ -19,8 +19,7 @@ import (
 // settingsKeys are the non-secret operational settings editable from the
 // Settings page. API credentials (Apify, eBay, ntfy, Resend) are deliberately
 // NOT here — they are managed only in config.toml on the server, so the UI
-// never reads or writes them. credentialStatus surfaces whether each is
-// configured, and the Test buttons verify them.
+// never reads or writes them. The Test buttons verify them.
 var settingsKeys = []string{
 	"ebay_daily_call_limit",
 	"ntfy_base_url",
@@ -29,29 +28,6 @@ var settingsKeys = []string{
 	"match_confidence_threshold",
 	"apify_cost_per_call",
 	"monthly_budget_usd",
-	"resend_from",
-}
-
-// credentialStatus reports, per credential, whether it is configured in
-// config.toml — without exposing the secret itself. ntfy_auth reflects the
-// Basic-auth user/password pair.
-func (a *App) credentialStatus() map[string]string {
-	configured := map[string]bool{
-		"apify_api_key":      strings.TrimSpace(a.Cfg.Apify.APIKey) != "",
-		"ebay_client_id":     strings.TrimSpace(a.Cfg.Ebay.ClientID) != "",
-		"ebay_client_secret": strings.TrimSpace(a.Cfg.Ebay.ClientSecret) != "",
-		"ntfy_auth":          strings.TrimSpace(a.Cfg.Ntfy.Username) != "" && a.Cfg.Ntfy.Password != "",
-		"resend_api_key":     strings.TrimSpace(a.Cfg.Resend.APIKey) != "",
-	}
-	status := make(map[string]string, len(configured))
-	for k, ok := range configured {
-		if ok {
-			status[k] = "Set in config.toml"
-		} else {
-			status[k] = "Not set"
-		}
-	}
-	return status
 }
 
 func (a *App) settingsData(r *http.Request) (templates.SettingsData, error) {
@@ -69,7 +45,6 @@ func (a *App) settingsData(r *http.Request) (templates.SettingsData, error) {
 	return templates.SettingsData{
 		Page:             a.page(r, "Settings", "settings"),
 		Values:           values,
-		CredentialStatus: a.credentialStatus(),
 		IsAdmin:          cur != nil && cur.Role == models.RoleAdmin,
 		Users:            users,
 		EbayUsedToday:    ebayUsed,
@@ -150,10 +125,7 @@ func (a *App) PostTestResend(w http.ResponseWriter, r *http.Request) {
 	if apiKey == "" {
 		apiKey = a.Cfg.Resend.APIKey
 	}
-	from := strings.TrimSpace(d.Values["resend_from"])
-	if from == "" {
-		from = a.Cfg.Resend.From
-	}
+	from := a.Cfg.Resend.From
 	to := ""
 	if cur != nil {
 		to = cur.Email