refactor: remove webmail interface, focus on core mail storage functionality

- Remove obsolete CouchDB design documents (webmail.json, dashboard.json)
- Clean up webmail-related code from couch/couch.go (WebmailViews, CreateWebmailViews, etc.)
- Update documentation to focus on core mail-to-CouchDB storage functionality
- Add Future Plans section describing planned webmail viewer as separate component
- Apply go fmt formatting and ensure code quality standards
- Update test documentation to show raw CouchDB API access patterns
- Remove compiled binary from repository

This refactor simplifies the codebase to focus on its core purpose: efficiently
backing up emails from IMAP to CouchDB. The webmail interface will be developed
as a separate, optional component to maintain clean separation of concerns.

🤖 Generated with [Claude Code](https://claude.ai/code)

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

go/mail/imap.go

@@ -104,7 +104,7 @@ func (c *ImapClient) GetMessages(mailbox string, since *time.Time, maxMessages i
 	// First, get all current UIDs in the mailbox for sync purposes
 	allUIDsSet := imap.SeqSet{}
 	allUIDsSet.AddRange(1, mbox.NumMessages)
-	
+
 	// Fetch UIDs for all messages to track current state
 	uidCmd := c.Fetch(allUIDsSet, &imap.FetchOptions{UID: true})
 	for {
@@ -112,12 +112,12 @@ func (c *ImapClient) GetMessages(mailbox string, since *time.Time, maxMessages i
 		if msg == nil {
 			break
 		}
-		
+
 		data, err := msg.Collect()
 		if err != nil {
 			continue
 		}
-		
+
 		if data.UID != 0 {
 			currentUIDs[uint32(data.UID)] = true
 		}
@@ -126,13 +126,13 @@ func (c *ImapClient) GetMessages(mailbox string, since *time.Time, maxMessages i
 
 	// Determine which messages to fetch based on since date
 	var seqSet imap.SeqSet
-	
+
 	if since != nil {
 		// Use IMAP SEARCH to find messages since the specified date
 		searchCriteria := &imap.SearchCriteria{
 			Since: *since,
 		}
-		
+
 		searchCmd := c.Search(searchCriteria, nil)
 		searchResults, err := searchCmd.Wait()
 		if err != nil {
@@ -149,12 +149,12 @@ func (c *ImapClient) GetMessages(mailbox string, since *time.Time, maxMessages i
 			if len(searchSeqNums) == 0 {
 				return []*Message{}, currentUIDs, nil
 			}
-			
+
 			// Limit results if maxMessages is specified
 			if maxMessages > 0 && len(searchSeqNums) > maxMessages {
 				searchSeqNums = searchSeqNums[len(searchSeqNums)-maxMessages:]
 			}
-			
+
 			for _, seqNum := range searchSeqNums {
 				seqSet.AddNum(seqNum)
 			}
@@ -165,11 +165,11 @@ func (c *ImapClient) GetMessages(mailbox string, since *time.Time, maxMessages i
 		if maxMessages > 0 && int(numToFetch) > maxMessages {
 			numToFetch = uint32(maxMessages)
 		}
-		
+
 		if numToFetch == 0 {
 			return []*Message{}, currentUIDs, nil
 		}
-		
+
 		// Fetch the most recent messages
 		seqSet.AddRange(mbox.NumMessages-numToFetch+1, mbox.NumMessages)
 	}
@@ -177,12 +177,12 @@ func (c *ImapClient) GetMessages(mailbox string, since *time.Time, maxMessages i
 	// Fetch message data - get envelope and full message body
 	options := &imap.FetchOptions{
 		Envelope: true,
-		UID: true,
+		UID:      true,
 		BodySection: []*imap.FetchItemBodySection{
 			{}, // Empty section gets the entire message
 		},
 	}
-	
+
 	fetchCmd := c.Fetch(seqSet, options)
 
 	for {
@@ -196,12 +196,12 @@ func (c *ImapClient) GetMessages(mailbox string, since *time.Time, maxMessages i
 			log.Printf("Failed to parse message: %v", err)
 			continue
 		}
-		
+
 		// Apply message-level keyword filtering
 		if messageFilter != nil && !c.ShouldProcessMessage(parsedMsg, messageFilter) {
 			continue // Skip this message due to keyword filter
 		}
-		
+
 		messages = append(messages, parsedMsg)
 	}
 
@@ -231,7 +231,7 @@ func (c *ImapClient) parseMessage(fetchMsg *imapclient.FetchMessageData) (*Messa
 		env := buffer.Envelope
 		msg.Subject = env.Subject
 		msg.Date = env.Date
-		
+
 		// Parse From addresses
 		for _, addr := range env.From {
 			if addr.Mailbox != "" {
@@ -242,7 +242,7 @@ func (c *ImapClient) parseMessage(fetchMsg *imapclient.FetchMessageData) (*Messa
 				msg.From = append(msg.From, fullAddr)
 			}
 		}
-		
+
 		// Parse To addresses
 		for _, addr := range env.To {
 			if addr.Mailbox != "" {
@@ -264,7 +264,7 @@ func (c *ImapClient) parseMessage(fetchMsg *imapclient.FetchMessageData) (*Messa
 	if len(buffer.BodySection) > 0 {
 		bodyBuffer := buffer.BodySection[0]
 		reader := bytes.NewReader(bodyBuffer.Bytes)
-		
+
 		// Parse the message using go-message
 		entity, err := message.Read(reader)
 		if err != nil {
@@ -338,7 +338,7 @@ func (c *ImapClient) parseMessagePart(entity *message.Entity, msg *Message) erro
 	disposition, dispositionParams, _ := entity.Header.ContentDisposition()
 
 	// Determine if this is an attachment
-	isAttachment := disposition == "attachment" || 
+	isAttachment := disposition == "attachment" ||
 		(disposition == "inline" && dispositionParams["filename"] != "") ||
 		params["name"] != ""