feat: add dark mode support for email viewer and related settings

frontend/messages/en.json

@@ -120,5 +120,8 @@
 	"settings_export_error": "Failed to export settings.",
 	"settings_import_success": "Settings imported successfully!",
 	"settings_import_error": "Failed to import settings.",
-	"settings_import_invalid": "Invalid settings file."
+	"settings_import_invalid": "Invalid settings file.",
+	"settings_email_dark_viewer_label": "Dark theme for email content",
+	"settings_email_dark_viewer_hint": "Display email body with a dark background matching the app theme.",
+	"settings_email_dark_viewer_info": "Info: When disabled, emails will display with their original light background. Some emails may be designed for light backgrounds and look better with this disabled."
 }

frontend/messages/it.json

@@ -120,5 +120,8 @@
 	"settings_export_error": "Impossibile esportare le impostazioni.",
 	"settings_import_success": "Impostazioni importate con successo!",
 	"settings_import_error": "Impossibile importare le impostazioni.",
-	"settings_import_invalid": "File impostazioni non valido."
+	"settings_import_invalid": "File impostazioni non valido.",
+	"settings_email_dark_viewer_label": "Tema scuro per contenuto email",
+	"settings_email_dark_viewer_hint": "Visualizza il corpo dell'email con uno sfondo scuro che corrisponde al tema dell'app.",
+	"settings_email_dark_viewer_info": "Info: Quando disabilitato, le email verranno visualizzate con lo sfondo chiaro originale. Alcune email potrebbero essere progettate per sfondi chiari e apparire meglio con questa opzione disabilitata."
 }

frontend/src/lib/components/MailViewer.svelte

@@ -20,7 +20,8 @@
 
   // Import refactored utilities
   import {
-    IFRAME_UTIL_HTML,
+    IFRAME_UTIL_HTML_DARK,
+    IFRAME_UTIL_HTML_LIGHT,
     CONTENT_TYPES,
     PEC_FILES,
     arrayBufferToBase64,
@@ -33,6 +34,7 @@
     processEmailBody,
     isEmailFile,
   } from '$lib/utils/mail';
+  import { settingsStore } from '$lib/stores/settings.svelte';
 
   // ============================================================================
   // State
@@ -42,6 +44,13 @@
   let isLoading = $state(false);
   let loadingText = $state('');
 
+  // Derived iframe HTML based on dark/light setting
+  let iframeUtilHtml = $derived(
+    settingsStore.settings.useDarkEmailViewer !== false
+      ? IFRAME_UTIL_HTML_DARK
+      : IFRAME_UTIL_HTML_LIGHT
+  );
+
   // ============================================================================
   // Event Handlers
   // ============================================================================
@@ -347,9 +356,9 @@
         </div>
 
         <!-- Email Body -->
-        <div class="email-body-wrapper">
+        <div class="email-body-wrapper" class:light-theme={settingsStore.settings.useDarkEmailViewer === false}>
           <iframe
-            srcdoc={mailState.currentEmail.body + IFRAME_UTIL_HTML}
+            srcdoc={mailState.currentEmail.body + iframeUtilHtml}
             title="Email Body"
             class="email-iframe"
             sandbox="allow-same-origin allow-scripts"
@@ -579,9 +588,15 @@
 
   .email-body-wrapper {
     flex: 1;
-    background: white;
+    background: #0d0d0d;
     position: relative;
     min-height: 200px;
+    border-radius: 0 0 14px 14px;
+    overflow: hidden;
+  }
+
+  .email-body-wrapper.light-theme {
+    background: #ffffff;
   }
 
   .email-iframe {

frontend/src/lib/stores/settings.svelte.ts

@@ -10,6 +10,7 @@ const defaults: EMLy_GUI_Settings = {
     useBuiltinPDFViewer: true,
     previewFileSupportedTypes: ["jpg", "jpeg", "png"],
     enableAttachedDebuggerProtection: true,
+    useDarkEmailViewer: true,
 };
 
 class SettingsStore {

frontend/src/lib/types.d.ts

@@ -8,6 +8,7 @@ interface EMLy_GUI_Settings {
     useBuiltinPDFViewer?: boolean;
     previewFileSupportedTypes?: SupportedFileTypePreview[];
     enableAttachedDebuggerProtection?: boolean;
+    useDarkEmailViewer?: boolean;
 }
 
 type SupportedLanguages = "en" | "it";

frontend/src/lib/utils/mail/constants.ts

@@ -1,10 +1,87 @@
 /**
- * HTML/CSS injected into the email body iframe for styling and security
+ * Dark theme HTML/CSS injected into the email body iframe
+ * - Applies dark theme matching the main app
+ * - Removes default body margins
+ * - Disables link clicking for security
+ * - Prevents Ctrl+Wheel zoom in iframe
+ * - Styles links, tables, and common email elements for dark mode
+ */
+export const IFRAME_UTIL_HTML_DARK = `<style>
+  body {
+    margin: 0;
+    padding: 20px;
+    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
+    background-color: #0d0d0d;
+    color: rgba(255, 255, 255, 0.9);
+    line-height: 1.5;
+  }
+  a {
+    pointer-events: none !important;
+    cursor: default !important;
+    color: #60a5fa !important;
+  }
+  img {
+    max-width: 100%;
+    height: auto;
+  }
+  table {
+    border-color: rgba(255, 255, 255, 0.15) !important;
+  }
+  td, th {
+    border-color: rgba(255, 255, 255, 0.15) !important;
+  }
+  hr {
+    border-color: rgba(255, 255, 255, 0.15);
+  }
+  blockquote {
+    border-left: 3px solid rgba(255, 255, 255, 0.2);
+    margin-left: 0;
+    padding-left: 16px;
+    color: rgba(255, 255, 255, 0.7);
+  }
+  pre, code {
+    background-color: rgba(255, 255, 255, 0.08);
+    border-radius: 4px;
+    padding: 2px 6px;
+  }
+  pre {
+    padding: 12px;
+    overflow-x: auto;
+  }
+</style><script>function handleWheel(event){if(event.ctrlKey){event.preventDefault();}}document.addEventListener('wheel',handleWheel,{passive:false});<\/script>`;
+
+/**
+ * Light theme HTML/CSS injected into the email body iframe (original styling)
+ * - Standard white background
  * - Removes default body margins
  * - Disables link clicking for security
  * - Prevents Ctrl+Wheel zoom in iframe
  */
-export const IFRAME_UTIL_HTML = `<style>body{margin:0;padding:20px;font-family:sans-serif;} a{pointer-events:none!important;cursor:default!important;}</style><script>function handleWheel(event){if(event.ctrlKey){event.preventDefault();}}document.addEventListener('wheel',handleWheel,{passive:false});<\/script>`;
+export const IFRAME_UTIL_HTML_LIGHT = `<style>
+  body {
+    margin: 0;
+    padding: 20px;
+    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
+    background-color: #ffffff;
+    color: #1a1a1a;
+    line-height: 1.5;
+  }
+  a {
+    pointer-events: none !important;
+    cursor: default !important;
+    color: #2563eb !important;
+  }
+  img {
+    max-width: 100%;
+    height: auto;
+  }
+</style><script>function handleWheel(event){if(event.ctrlKey){event.preventDefault();}}document.addEventListener('wheel',handleWheel,{passive:false});<\/script>`;
+
+/**
+ * Default iframe HTML (dark theme for backwards compatibility)
+ * @deprecated Use IFRAME_UTIL_HTML_DARK or IFRAME_UTIL_HTML_LIGHT instead
+ */
+export const IFRAME_UTIL_HTML = IFRAME_UTIL_HTML_DARK;
 
 /**
  * Supported email file extensions

frontend/src/lib/utils/mail/index.ts

@@ -5,6 +5,8 @@
 // Constants
 export {
   IFRAME_UTIL_HTML,
+  IFRAME_UTIL_HTML_DARK,
+  IFRAME_UTIL_HTML_LIGHT,
   EMAIL_EXTENSIONS,
   CONTENT_TYPES,
   PEC_FILES,

frontend/src/routes/(app)/settings/+page.svelte

@@ -38,6 +38,7 @@
     useBuiltinPDFViewer: true,
     previewFileSupportedTypes: ["jpg", "jpeg", "png"],
     enableAttachedDebuggerProtection: true,
+    useDarkEmailViewer: true,
   };
 
   async function setLanguage(
@@ -68,6 +69,8 @@
         s.previewFileSupportedTypes || defaults.previewFileSupportedTypes || [],
       enableAttachedDebuggerProtection:
         s.enableAttachedDebuggerProtection ?? defaults.enableAttachedDebuggerProtection ?? true,
+      useDarkEmailViewer:
+        s.useDarkEmailViewer ?? defaults.useDarkEmailViewer ?? true,
     };
   }
 
@@ -77,6 +80,7 @@
       !!a.useBuiltinPreview === !!b.useBuiltinPreview &&
       !!a.useBuiltinPDFViewer === !!b.useBuiltinPDFViewer &&
       !!a.enableAttachedDebuggerProtection === !!b.enableAttachedDebuggerProtection &&
+      !!a.useDarkEmailViewer === !!b.useDarkEmailViewer &&
       JSON.stringify(a.previewFileSupportedTypes?.sort()) ===
         JSON.stringify(b.previewFileSupportedTypes?.sort())
     );
@@ -450,6 +454,29 @@
             {m.settings_preview_pdf_builtin_info()}
           </p>
         </div>
+        <Separator />
+
+        <div class="space-y-3">
+          <div
+            class="flex items-center justify-between gap-4 rounded-lg border bg-card p-4"
+          >
+            <div>
+              <div class="font-medium">
+                {m.settings_email_dark_viewer_label()}
+              </div>
+              <div class="text-sm text-muted-foreground">
+                {m.settings_email_dark_viewer_hint()}
+              </div>
+            </div>
+            <Switch
+              bind:checked={form.useDarkEmailViewer}
+              class="cursor-pointer hover:cursor-pointer"
+            />
+          </div>
+          <p class="text-xs text-muted-foreground mt-2">
+            {m.settings_email_dark_viewer_info()}
+          </p>
+        </div>
       </Card.Content>
     </Card.Root>