refactor: parallelize KV writes, cap metadata, remove redundant normalization

- email-processor: run email put + metadata get in parallel (saves one KV round-trip per email)
- email-processor: add missing 50-email metadata cap (was unbounded unlike storage.ts)
- email-processor: remove redundant normalizeEmail call on already-normalized allowedSender
- email-parser: strip WHAT-comments and boilerplate JSDoc throughout

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

src/utils/email-parser.ts

@@ -1,48 +1,26 @@
 import { EmailData } from "../types";
 
-/**
- * Simple email parser specialized for ForwardEmail.net's webhook format
- */
 export class EmailParser {
-  /**
-   * Extract the feed ID from an email address
-   * @param emailAddress The email address (e.g., apple.mountain.42@domain.com)
-   * @returns The feed ID or null if not found
-   */
+  // Matches noun1.noun2.XY (the feed ID format) before the @ symbol
   static extractFeedId(emailAddress: string): string | null {
-    // Match pattern for noun1.noun2.XY before the @ symbol
     const match = emailAddress.match(/^([a-z]+\.[a-z]+\.\d{2})@/i);
     return match ? match[1] : null;
   }
 
-  /**
-   * Parse email data from ForwardEmail.net's webhook payload
-   * @param payload ForwardEmail.net webhook payload
-   */
   static parseForwardEmailPayload(payload: any): EmailData {
     if (!payload) {
       throw new Error("Missing or invalid webhook payload");
     }
 
-    // Extract the "to" address
-    const toAddress = payload.recipients?.[0] || "";
-
-    // Extract the sender information using ForwardEmail's structure
     const fromAddress =
       payload.from?.text ||
       (payload.from?.value?.[0]?.address
         ? `${payload.from.value[0].name || ""} <${payload.from.value[0].address}>`
         : "Unknown Sender");
 
-    // Extract subject
-    let subject = payload.subject || "No Subject";
-    // Decode any encoded words in the subject
-    subject = this.decodeEncodedWords(subject);
-
-    // Get content, preferring HTML over plain text
+    const subject = this.decodeEncodedWords(payload.subject || "No Subject");
     const content = payload.html || payload.text || "";
 
-    // Create simple email data object
     return {
       subject,
       from: fromAddress,
@@ -52,13 +30,9 @@ export class EmailParser {
     };
   }
 
-  /**
-   * Extract headers from ForwardEmail payload
-   */
   private static extractHeaders(payload: any): Record<string, string> {
     const headers: Record<string, string> = {};
 
-    // Extract headers from headerLines if available
     if (payload.headerLines && Array.isArray(payload.headerLines)) {
       payload.headerLines.forEach((h: { key: string; line: string }) => {
         const key = h.key.toLowerCase();
@@ -67,9 +41,7 @@ export class EmailParser {
           .trim();
         headers[key] = value;
       });
-    }
-    // Or from headers string if provided
-    else if (typeof payload.headers === "string") {
+    } else if (typeof payload.headers === "string") {
       payload.headers.split(/\r?\n/).forEach((line: string) => {
         const match = line.match(/^([^:]+):\s*(.*)$/);
         if (match) {
@@ -81,27 +53,19 @@ export class EmailParser {
     return headers;
   }
 
-  /**
-   * Decode RFC 2047 encoded words in headers
-   * @param text Text that may contain encoded words like =?UTF-8?Q?Hello_World?=
-   */
   static decodeEncodedWords(text: string): string {
     if (!text) return "";
 
-    // Simple RFC 2047 encoded-word decoder
     return text.replace(
       /=\?([^?]+)\?([BQ])\?([^?]+)\?=/gi,
       (_, charset, encoding, text) => {
         if (encoding.toUpperCase() === "B") {
-          // Base64 encoding
           try {
-            const decoded = atob(text);
-            return decoded;
+            return atob(text);
           } catch (e) {
             return text;
           }
         } else if (encoding.toUpperCase() === "Q") {
-          // Quoted-printable encoding
           return this.decodeQuotedPrintable(text.replace(/_/g, " "));
         }
         return text;
@@ -109,10 +73,6 @@ export class EmailParser {
     );
   }
 
-  /**
-   * Decode quoted-printable encoded text
-   * @param text Quoted-printable encoded text
-   */
   private static decodeQuotedPrintable(text: string): string {
     return text.replace(/=([0-9A-F]{2})/gi, (_, hex) => {
       return String.fromCharCode(parseInt(hex, 16));