email: charset decoding, inline attachments, UI fixes

- respect charset from Content-Type when decoding body and headers
- detect inline attachments with filenames (not just disposition: attachment)
- fix broken decodeQuotedPrintable reference in parseAttachments
- white background for email iframe (emails designed for light bg)
- sticky header in email list, scrollable message area
- arrow key navigation between emails with scroll-into-view
- /email/:id routing for deep linking to specific emails
- empty folder shows "No emails in this folder" instead of losing header
- fix attachment viewer header overlap with dialog close button

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/servers/api/email/email-db.ts

@@ -251,10 +251,12 @@ export function updateEmailLabels(db: Database, id: string, labels: string[]): v
 // ── Header parsing helpers (same logic as gmail-sync) ──
 
 function decodeMimeWords(text: string): string {
-  return text.replace(/=\?([^?]+)\?(B|Q)\?([^?]+)\?=/gi, (_, _charset, encoding, encoded) => {
+  return text.replace(/=\?([^?]+)\?(B|Q)\?([^?]+)\?=/gi, (_, charset, encoding, encoded) => {
     try {
+      const normalizedCs = normalizeCharset(charset.toLowerCase());
       if (encoding.toUpperCase() === 'B') {
-        return Buffer.from(encoded, 'base64').toString('utf-8');
+        const buf = Buffer.from(encoded, 'base64');
+        return new TextDecoder(normalizedCs, { fatal: false }).decode(buf);
       }
       const bytes: number[] = [];
       for (let i = 0; i < encoded.length; i++) {
@@ -267,7 +269,7 @@ function decodeMimeWords(text: string): string {
           bytes.push(encoded.charCodeAt(i));
         }
       }
-      return Buffer.from(bytes).toString('utf-8');
+      return new TextDecoder(normalizedCs, { fatal: false }).decode(Buffer.from(bytes));
     } catch {
       return encoded;
     }
@@ -325,16 +327,51 @@ function extractSnippet(raw: string): string {
   return body.replace(/\s+/g, ' ').trim().slice(0, 120);
 }
 
-function decodeQuotedPrintable(text: string): string {
-  return text
-    .replace(/=\r?\n/g, '')
-    .replace(/=([0-9A-Fa-f]{2})/g, (_, hex) => String.fromCharCode(parseInt(hex, 16)));
+function decodeQuotedPrintableBytes(text: string): Buffer {
+  const cleaned = text.replace(/=\r?\n/g, '');
+  const bytes: number[] = [];
+  for (let i = 0; i < cleaned.length; i++) {
+    if (cleaned[i] === '=' && i + 2 < cleaned.length) {
+      const hex = cleaned.slice(i + 1, i + 3);
+      const val = parseInt(hex, 16);
+      if (!isNaN(val)) {
+        bytes.push(val);
+        i += 2;
+        continue;
+      }
+    }
+    bytes.push(cleaned.charCodeAt(i));
+  }
+  return Buffer.from(bytes);
 }
 
-function decodePartBody(body: string, encoding: string): string {
+function extractCharset(contentType: string): string {
+  const match = contentType.match(/charset=["']?([^"';\s]+)/i);
+  return match?.[1]?.toLowerCase() ?? 'utf-8';
+}
+
+function normalizeCharset(charset: string): string {
+  const map: Record<string, string> = {
+    'iso-8859-1': 'latin1',
+    'iso_8859-1': 'latin1',
+    'windows-1252': 'latin1',
+    'us-ascii': 'ascii',
+    'ascii': 'ascii',
+  };
+  return map[charset] ?? charset;
+}
+
+function decodePartBody(body: string, encoding: string, charset = 'utf-8'): string {
   const enc = encoding.toLowerCase();
-  if (enc === 'base64') return Buffer.from(body.replace(/\s/g, ''), 'base64').toString('utf-8');
-  if (enc === 'quoted-printable') return decodeQuotedPrintable(body);
+  const normalizedCharset = normalizeCharset(charset);
+  if (enc === 'base64') {
+    const buf = Buffer.from(body.replace(/\s/g, ''), 'base64');
+    return new TextDecoder(normalizedCharset, { fatal: false }).decode(buf);
+  }
+  if (enc === 'quoted-printable') {
+    const buf = decodeQuotedPrintableBytes(body);
+    return new TextDecoder(normalizedCharset, { fatal: false }).decode(buf);
+  }
   return body;
 }
 
@@ -349,7 +386,8 @@ function extractBody(raw: string): { html: string | null; text: string | null }
   // Non-multipart: single body
   if (!topCt.includes('multipart')) {
     const body = raw.slice(headerEnd);
-    const decoded = decodePartBody(body, topEncoding);
+    const charset = extractCharset(topCtRaw);
+    const decoded = decodePartBody(body, topEncoding, charset);
     if (topCt.includes('text/html')) return { html: decoded, text: null };
     return { html: null, text: decoded };
   }
@@ -368,8 +406,10 @@ function extractBody(raw: string): { html: string | null; text: string | null }
     const partHeaderEnd = findHeaderEnd(part);
     if (partHeaderEnd === -1) continue;
 
-    const partCt = extractFullHeader(part, 'Content-Type').toLowerCase();
+    const partCtRaw = extractFullHeader(part, 'Content-Type');
+    const partCt = partCtRaw.toLowerCase();
     const partEnc = extractFullHeader(part, 'Content-Transfer-Encoding');
+    const partCharset = extractCharset(partCtRaw);
     const partBody = part.slice(partHeaderEnd);
 
     // Recurse into nested multipart (e.g. multipart/alternative inside multipart/mixed)
@@ -381,9 +421,9 @@ function extractBody(raw: string): { html: string | null; text: string | null }
     }
 
     if (partCt.includes('text/html') && !html) {
-      html = decodePartBody(partBody, partEnc);
+      html = decodePartBody(partBody, partEnc, partCharset);
     } else if (partCt.includes('text/plain') && !text) {
-      text = decodePartBody(partBody, partEnc);
+      text = decodePartBody(partBody, partEnc, partCharset);
     }
   }
 
@@ -394,7 +434,8 @@ type AttachmentMeta = { filename: string; size: number; contentType: string; con
 
 function parseAttachments(raw: string): AttachmentMeta[] {
   const results: AttachmentMeta[] = [];
-  const regex = /^Content-Disposition:\s*attachment[^\n]*/gim;
+  // Match both "attachment" and "inline" dispositions
+  const regex = /^Content-Disposition:\s*(?:attachment|inline)[^\n]*/gim;
   let match: RegExpExecArray | null;
 
   while ((match = regex.exec(raw)) !== null) {
@@ -404,6 +445,10 @@ function parseAttachments(raw: string): AttachmentMeta[] {
     const partStart = raw.lastIndexOf('\n--', pos);
     const headerBlock = partStart !== -1 ? raw.slice(partStart, pos + 500) : raw.slice(Math.max(0, pos - 500), pos + 500);
 
+    // Skip inline parts without a filename (e.g. inline text/plain body parts)
+    const hasFilename = /filename/i.test(headerBlock);
+    if (!hasFilename) continue;
+
     // Extract filename from Content-Disposition or Content-Type
     const fnMatch = headerBlock.match(/filename\*?=(?:"([^"]+)"|([^\s;]+))/i);
     const filename = fnMatch ? (fnMatch[1] ?? fnMatch[2] ?? 'unknown') : 'unknown';
@@ -430,7 +475,7 @@ function parseAttachments(raw: string): AttachmentMeta[] {
       } else {
         // For quoted-printable or 7bit/8bit, re-encode to base64
         const buf = encoding === 'quoted-printable'
-          ? Buffer.from(decodeQuotedPrintable(bodyRaw))
+          ? decodeQuotedPrintableBytes(bodyRaw)
           : Buffer.from(bodyRaw);
         content = buf.toString('base64');
       }