fix(ui): resolve light-theme low-contrast semantic text app-wide (#1909)

The app was built dark-first, so hundreds of hardcoded Tailwind semantic
text/icon utilities at light shades (text-amber-400, text-blue-300, ...) had
no dark: variant. With darkMode:'class' they applied in light theme too,
producing washed-out text on pale tints and white cards — including the three
reported spots (AMS Drying banner, Archives no-3MF warning, debug-logging
banner). Give each a theme-aware pair: a darker readable shade in light theme
with the original pinned to dark:, so dark theme is unchanged. ~100 files.

The bambu-* CSS-variable palette (self-correcting) and the dark-only SpoolBuddy
kiosk are left untouched. Plain text-white is already theme-aware via the
existing index.css .text-white override, so it needed no changes.

frontend/src/components/AddSmartPlugModal.tsx

@@ -431,7 +431,7 @@ export function AddSmartPlugModal({ plug, onClose }: AddSmartPlugModalProps) {
         {/* Form */}
         <form onSubmit={handleSubmit} className="p-6 space-y-4 overflow-y-auto">
           {error && (
-            <div className="p-3 bg-red-500/20 border border-red-500/50 rounded-lg text-sm text-red-400">
+            <div className="p-3 bg-red-100 dark:bg-red-500/20 border border-red-400 dark:border-red-500/50 rounded-lg text-sm text-red-700 dark:text-red-400">
               {error}
             </div>
           )}
@@ -585,7 +585,7 @@ export function AddSmartPlugModal({ plug, onClose }: AddSmartPlugModalProps) {
               {/* HA not configured */}
               {!haConfigured && (
                 <div className="space-y-3">
-                  <div className="p-3 bg-yellow-500/20 border border-yellow-500/50 rounded-lg text-sm text-yellow-400">
+                  <div className="p-3 bg-yellow-100 dark:bg-yellow-500/20 border border-yellow-400 dark:border-yellow-500/50 rounded-lg text-sm text-yellow-700 dark:text-yellow-400">
                     {t('smartPlugs.haNotConfigured')}{' '}
                     <span className="font-medium">{t('smartPlugs.haSettingsPath')}</span>
                   </div>
@@ -612,7 +612,7 @@ export function AddSmartPlugModal({ plug, onClose }: AddSmartPlugModalProps) {
                   )}
 
                   {haEntitiesError && (
-                    <div className="p-3 bg-red-500/20 border border-red-500/50 rounded-lg text-sm text-red-400">
+                    <div className="p-3 bg-red-100 dark:bg-red-500/20 border border-red-400 dark:border-red-500/50 rounded-lg text-sm text-red-700 dark:text-red-400">
                       {t('smartPlugs.failedToLoadEntities', { error: (haEntitiesError as Error).message })}
                     </div>
                   )}
@@ -988,7 +988,7 @@ export function AddSmartPlugModal({ plug, onClose }: AddSmartPlugModalProps) {
             <div className="space-y-3">
               {/* MQTT broker not configured */}
               {!settings?.mqtt_broker && (
-                <div className="p-3 bg-yellow-500/20 border border-yellow-500/50 rounded-lg text-sm text-yellow-400">
+                <div className="p-3 bg-yellow-100 dark:bg-yellow-500/20 border border-yellow-400 dark:border-yellow-500/50 rounded-lg text-sm text-yellow-700 dark:text-yellow-400">
                   {t('smartPlugs.mqttNotConfigured')}{' '}
                   <span className="font-medium">{t('smartPlugs.mqttSettingsPath')}</span>
                   {' '}{t('smartPlugs.mqttNotConfiguredSuffix')}
@@ -998,7 +998,7 @@ export function AddSmartPlugModal({ plug, onClose }: AddSmartPlugModalProps) {
               {/* MQTT broker configured - show fields */}
               {settings?.mqtt_broker && (
                 <>
-                  <div className="p-3 bg-blue-500/10 border border-blue-500/30 rounded-lg text-sm text-blue-300">
+                  <div className="p-3 bg-blue-50 dark:bg-blue-500/10 border border-blue-300 dark:border-blue-500/30 rounded-lg text-sm text-blue-700 dark:text-blue-300">
                     <p className="font-medium mb-1">{t('smartPlugs.monitorOnly')}</p>
                     <p className="text-xs opacity-80">
                       {t('smartPlugs.mqttMonitorOnlyDescription')}
@@ -1346,7 +1346,7 @@ export function AddSmartPlugModal({ plug, onClose }: AddSmartPlugModalProps) {
                 </div>
               )}
               {testResult && (
-                <div className={`flex items-center gap-2 text-sm ${testResult.success ? 'text-green-400' : 'text-red-400'}`}>
+                <div className={`flex items-center gap-2 text-sm ${testResult.success ? 'text-green-700 dark:text-green-400' : 'text-red-700 dark:text-red-400'}`}>
                   {testResult.success ? <CheckCircle className="w-4 h-4" /> : <WifiOff className="w-4 h-4" />}
                   {testResult.success ? t('smartPlugs.connectionSuccess') : t('smartPlugs.addSmartPlug.connectionFailed')}
                 </div>
@@ -1391,7 +1391,7 @@ export function AddSmartPlugModal({ plug, onClose }: AddSmartPlugModalProps) {
             <div className={`p-3 rounded-lg flex items-center gap-2 ${
               testResult.success
                 ? 'bg-bambu-green/20 border border-bambu-green/50 text-bambu-green'
-                : 'bg-red-500/20 border border-red-500/50 text-red-400'
+                : 'bg-red-100 dark:bg-red-500/20 border border-red-400 dark:border-red-500/50 text-red-700 dark:text-red-400'
             }`}>
               {testResult.success ? (
                 <>