Add email sync service for automated job application tracking

Background poller fetches emails via IMAP or Microsoft Graph API,
classifies them with Claude Haiku, and creates/updates JobApplication
records automatically. Includes manual sync endpoint and OAuth callback.

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

backend/services/email_imap.go

@@ -0,0 +1,133 @@
+package services
+
+import (
+	"fmt"
+	"io"
+	"log"
+	"time"
+
+	"github.com/emersion/go-imap/v2"
+	"github.com/emersion/go-imap/v2/imapclient"
+)
+
+type IMAPConfig struct {
+	Host     string
+	Port     string
+	Email    string
+	Password string
+}
+
+// fetchEmailsIMAP connects to an IMAP server and retrieves emails since the given time.
+func (s *EmailSyncService) fetchEmailsIMAP(since time.Time) ([]graphMessage, error) {
+	addr := fmt.Sprintf("%s:%s", s.Config.IMAP.Host, s.Config.IMAP.Port)
+
+	c, err := imapclient.DialTLS(addr, nil)
+	if err != nil {
+		return nil, fmt.Errorf("IMAP connect: %w", err)
+	}
+	defer c.Close()
+
+	if err := c.Login(s.Config.IMAP.Email, s.Config.IMAP.Password).Wait(); err != nil {
+		return nil, fmt.Errorf("IMAP login: %w", err)
+	}
+
+	if _, err := c.Select("INBOX", nil).Wait(); err != nil {
+		return nil, fmt.Errorf("IMAP select INBOX: %w", err)
+	}
+
+	// Search for emails since the given time
+	sinceDate := since.UTC()
+	searchCriteria := &imap.SearchCriteria{
+		Since: sinceDate,
+	}
+	searchData, err := c.Search(searchCriteria, nil).Wait()
+	if err != nil {
+		return nil, fmt.Errorf("IMAP search: %w", err)
+	}
+
+	if searchData.AllSeqNums() == nil || len(searchData.AllSeqNums()) == 0 {
+		return nil, nil
+	}
+
+	seqNums := searchData.AllSeqNums()
+	log.Printf("[EmailSync/IMAP] Found %d messages since %s", len(seqNums), sinceDate.Format(time.RFC3339))
+
+	seqSet := imap.SeqSetNum(seqNums...)
+	fetchOptions := &imap.FetchOptions{
+		Envelope:    true,
+		BodySection: []*imap.FetchItemBodySection{{}},
+	}
+
+	fetchCmd := c.Fetch(seqSet, fetchOptions)
+	defer fetchCmd.Close()
+
+	var messages []graphMessage
+
+	for {
+		msg := fetchCmd.Next()
+		if msg == nil {
+			break
+		}
+
+		var envelope *imap.Envelope
+		var bodyContent string
+
+		for {
+			item := msg.Next()
+			if item == nil {
+				break
+			}
+
+			switch data := item.(type) {
+			case imapclient.FetchItemDataEnvelope:
+				envelope = data.Envelope
+			case imapclient.FetchItemDataBodySection:
+				body, err := io.ReadAll(data.Literal)
+				if err != nil {
+					log.Printf("[EmailSync/IMAP] Error reading body: %v", err)
+					continue
+				}
+				bodyContent = string(body)
+			}
+		}
+
+		if envelope == nil {
+			continue
+		}
+
+		// Convert to graphMessage format for unified processing
+		var fromName, fromAddr string
+		if len(envelope.From) > 0 {
+			fromName = envelope.From[0].Name
+			fromAddr = envelope.From[0].Addr()
+		}
+
+		gm := graphMessage{
+			ID:               envelope.MessageID,
+			Subject:          envelope.Subject,
+			ReceivedDateTime: envelope.Date.Format(time.RFC3339),
+			From: graphFrom{
+				EmailAddress: graphEmailAddress{
+					Name:    fromName,
+					Address: fromAddr,
+				},
+			},
+			Body: graphBody{
+				ContentType: "text",
+				Content:     bodyContent,
+			},
+		}
+
+		messages = append(messages, gm)
+	}
+
+	if err := fetchCmd.Close(); err != nil {
+		return nil, fmt.Errorf("IMAP fetch: %w", err)
+	}
+
+	if err := c.Logout().Wait(); err != nil {
+		log.Printf("[EmailSync/IMAP] Logout error: %v", err)
+	}
+
+	return messages, nil
+}