refactor: split src into domain / application / infrastructure layers

Replace the history-driven lib/ + utils/ split with DDD layers:
- domain/: aggregate, repositories, value objects, pure parsers/format
- application/: feed-service, email-processor, feed-fetcher, stats
- infrastructure/: logging, auth, KV/R2 adapters, HTTP, framework glue

Pure file relocation; imports updated mechanically. Behaviour unchanged.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

src/domain/email-parser.ts

@@ -0,0 +1,83 @@
+import { EmailData } from "../types";
+import { FeedId } from "../domain/value-objects/feed-id";
+
+export class EmailParser {
+  // Matches noun1.noun2.XY (the feed ID format) before the @ symbol
+  static extractFeedId(emailAddress: string): string | null {
+    return FeedId.parse(emailAddress)?.value ?? null;
+  }
+
+  // eslint-disable-next-line @typescript-eslint/no-explicit-any
+  static parseForwardEmailPayload(payload: any): EmailData {
+    if (!payload) {
+      throw new Error("Missing or invalid webhook payload");
+    }
+
+    const fromAddress =
+      payload.from?.text ||
+      (payload.from?.value?.[0]?.address
+        ? `${payload.from.value[0].name || ""} <${payload.from.value[0].address}>`
+        : "Unknown Sender");
+
+    const subject = this.decodeEncodedWords(payload.subject || "No Subject");
+    const content = payload.html || payload.text || "";
+
+    return {
+      subject,
+      from: fromAddress,
+      content,
+      receivedAt: payload.date ? new Date(payload.date).getTime() : Date.now(),
+      headers: this.extractHeaders(payload),
+    };
+  }
+
+  // eslint-disable-next-line @typescript-eslint/no-explicit-any
+  private static extractHeaders(payload: any): Record<string, string> {
+    const headers: Record<string, string> = {};
+
+    if (payload.headerLines && Array.isArray(payload.headerLines)) {
+      payload.headerLines.forEach((h: { key: string; line: string }) => {
+        const key = h.key.toLowerCase();
+        const value = h.line
+          .replace(new RegExp(`^${h.key}:\\s*`, "i"), "")
+          .trim();
+        headers[key] = value;
+      });
+    } else if (typeof payload.headers === "string") {
+      payload.headers.split(/\r?\n/).forEach((line: string) => {
+        const match = line.match(/^([^:]+):\s*(.*)$/);
+        if (match) {
+          headers[match[1].toLowerCase()] = match[2];
+        }
+      });
+    }
+
+    return headers;
+  }
+
+  static decodeEncodedWords(text: string): string {
+    if (!text) return "";
+
+    return text.replace(
+      /=\?([^?]+)\?([BQ])\?([^?]+)\?=/gi,
+      (_, charset, encoding, text) => {
+        if (encoding.toUpperCase() === "B") {
+          try {
+            return atob(text);
+          } catch {
+            return text;
+          }
+        } else if (encoding.toUpperCase() === "Q") {
+          return this.decodeQuotedPrintable(text.replace(/_/g, " "));
+        }
+        return text;
+      },
+    );
+  }
+
+  private static decodeQuotedPrintable(text: string): string {
+    return text.replace(/=([0-9A-F]{2})/gi, (_, hex) => {
+      return String.fromCharCode(parseInt(hex, 16));
+    });
+  }
+}