feat(cli): add interactive email import tool for EML, MBOX, and Thunderbird

- Implement `bichonctl` interactive CLI using `dialoguer`.
- Support recursive EML directory scanning with folder structure preservation.
- Support single MBOX file streaming import.
- Support Thunderbird profile import with automatic `.sbd` hierarchy detection.
- Add batch processing (Base64 encoding & batch API requests) for improved performance.

src/modules/cli/mbox/mod.rs

@@ -0,0 +1,145 @@
+use std::collections::HashMap;
+use std::path::PathBuf;
+
+use crate::base64_encode_url_safe;
+use crate::modules::cli::mbox::gmail::determine_folder;
+use crate::modules::cli::mbox::reader::MboxFile;
+use crate::modules::cli::sender::send_batch_request;
+use crate::modules::cli::BichonCtlConfig;
+use console::style;
+use dialoguer::{theme::ColorfulTheme, Input};
+use dialoguer::{Confirm, Select};
+use mail_parser::MessageParser;
+use reqwest::Client;
+
+pub mod gmail;
+pub mod reader;
+
+pub async fn handle_mbox_single_file_import(
+    config: &BichonCtlConfig,
+    account_id: u64,
+    theme: &ColorfulTheme,
+) {
+    let path_str: String = Input::with_theme(theme)
+        .with_prompt("Enter the path to your SINGLE .mbox file")
+        .validate_with(|input: &String| {
+            let p = std::path::Path::new(input);
+            if !p.exists() {
+                return Err("The specified path does not exist.");
+            }
+            if !p.is_file() {
+                return Err("MBOX mode requires a SINGLE file, not a directory.");
+            }
+            Ok(())
+        })
+        .interact_text()
+        .unwrap();
+
+    let mbox_path = PathBuf::from(path_str);
+
+    let options = vec![
+        "Use labels from mail headers (X-Gmail-Labels)",
+        "Specify a single target folder for all emails",
+    ];
+
+    let selection = Select::with_theme(theme)
+        .with_prompt("How should we determine the target folder?")
+        .items(&options)
+        .default(0)
+        .interact()
+        .unwrap();
+
+    let target_folder: Option<String> = match selection {
+        0 => None,
+        1 => {
+            let folder: String = Input::with_theme(theme)
+                .with_prompt("Target folder name")
+                .default("INBOX".into())
+                .interact_text()
+                .unwrap();
+            Some(folder)
+        }
+        _ => unreachable!(),
+    };
+
+    if let Some(ref folder) = target_folder {
+        println!(
+            "{}",
+            style(format!("Mode: Fixed folder ({})", folder)).dim()
+        );
+    } else {
+        println!("{}", style("Mode: Dynamic (header-based)").dim());
+    }
+
+    println!(
+        "\n{} Ready to process MBOX file: {}",
+        style("✔").green(),
+        style(mbox_path.display()).cyan()
+    );
+
+    if let Ok(meta) = std::fs::metadata(&mbox_path) {
+        let size_mb = meta.len() as f64 / 1024.0 / 1024.0;
+        println!(
+            "{}",
+            style(format!("Processing file: {:.1} MB", size_mb)).dim()
+        );
+    }
+
+    if Confirm::with_theme(theme)
+        .with_prompt("Start importing?")
+        .default(true)
+        .interact()
+        .unwrap()
+    {
+        run_import(account_id, &mbox_path, config, target_folder).await
+    }
+}
+
+pub async fn run_import(
+    account_id: u64,
+    mbox_path: &PathBuf,
+    config: &BichonCtlConfig,
+    target_folder: Option<String>,
+) {
+    let client = Client::new();
+    let mbox = MboxFile::from_file(mbox_path).unwrap();
+
+    let mut folder_buffers: HashMap<String, Vec<String>> = HashMap::new();
+    let batch_limit = 50;
+
+    println!("Starting import process...");
+
+    for e in mbox.iter() {
+        let body = e.data;
+        let message = MessageParser::new().parse(body).unwrap();
+
+        let folder_name = match target_folder {
+            Some(ref folder_name) => folder_name.clone(),
+            None => {
+                let labels = message
+                    .header("X-Gmail-Labels")
+                    .and_then(|h| h.as_text())
+                    .unwrap_or("Inbox");
+                determine_folder(labels)
+            }
+        };
+        let b64_eml = base64_encode_url_safe!(&body);
+        let buffer = folder_buffers
+            .entry(folder_name.clone())
+            .or_insert_with(|| Vec::new());
+        buffer.push(b64_eml);
+
+        if buffer.len() >= batch_limit {
+            let emls_to_send = folder_buffers.remove(&folder_name).unwrap();
+            send_batch_request(&client, config, account_id, &folder_name, emls_to_send).await;
+        }
+    }
+
+    for (folder_name, emls) in folder_buffers {
+        if !emls.is_empty() {
+            send_batch_request(&client, config, account_id, &folder_name, emls).await;
+        }
+    }
+
+    println!("{}", style("Import completed successfully!").green().bold());
+}