feat(api): extract pure API clients for image generation and TTS

- Add bin/api/ package with generate_image() and synthesize_tts()
- Refactor bin/commands/image.py to call bin.api.image.generate_image
- Refactor bin/commands/voice.py to call bin.api.voice.synthesize_tts
- API layer is free of Click CLI dependencies, usable by external scripts

bin/commands/image.py

@@ -1,13 +1,11 @@
 """Image utilities."""
 
-import base64
-import os
 import subprocess
-import urllib.request
 from pathlib import Path
 
 import click
 
+from bin.api.image import _RATIO_MAP, generate_image
 from bin.config import config
 from bin.utils import handle_errors, run_command
 
@@ -187,15 +185,6 @@ def compress_images(files, target_mb, max_width, quality, suffix, dry_run):
             click.echo(f"Compressed: {img_file} -> {output} ({size_mb:.2f} MB)")
 
 
-_RATIO_MAP = {
-    "1:1": "1024x1024",
-    "4:3": "1024x768",
-    "3:4": "768x1024",
-    "16:9": "1280x720",
-    "9:16": "720x1280",
-}
-
-
 @image.command("generate")
 @click.argument("prompt", required=False)
 @click.option("-f", "--file", type=click.Path(exists=True), help="从文件读取 prompt")
@@ -207,8 +196,6 @@ _RATIO_MAP = {
 @handle_errors
 def generate_image_cmd(prompt, file, size, ratio, output, no_watermark, b64):
     """使用豆包/Seedream 模型生成图片。"""
-    from openai import OpenAI
-
     if file:
         prompt = Path(file).read_text(encoding="utf-8").strip()
     elif not prompt:
@@ -222,30 +209,13 @@ def generate_image_cmd(prompt, file, size, ratio, output, no_watermark, b64):
     if size and ratio:
         click.echo("Warning: --size 和 --ratio 同时指定，--size 优先", err=True)
 
-    resolved_size = size or (ratio and _RATIO_MAP[ratio]) or "2K"
-
-    client = OpenAI(
-        base_url="https://ark.cn-beijing.volces.com/api/v3",
+    result = generate_image(
         api_key=api_key,
-    )
-
-    resp = client.images.generate(
-        model="doubao-seedream-5-0-260128",
         prompt=prompt,
-        size=resolved_size,
-        response_format="b64_json" if b64 else "url",
-        extra_body={"watermark": not no_watermark},
+        size=size,
+        ratio=ratio,
+        output=output,
+        watermark=not no_watermark,
+        b64=b64,
     )
-
-    if b64:
-        image_bytes = base64.b64decode(resp.data[0].b64_json)
-        save_path = output or "generated_image.png"
-        Path(save_path).write_bytes(image_bytes)
-        click.echo(os.path.abspath(save_path))
-    else:
-        url = resp.data[0].url
-        if output:
-            urllib.request.urlretrieve(url, output)
-            click.echo(os.path.abspath(output))
-        else:
-            click.echo(url)
+    click.echo(result)