Add selectable animdl download fallback

http_handler.py

@@ -20,6 +20,7 @@ from pathlib import Path
 from urllib.parse import parse_qs, unquote, urlencode, urlparse, urlunparse
 
 from app_support import (
+    ANIMDL,
     ANI_CLI,
     ANIPY_CLI,
     APP_NAME,
@@ -94,6 +95,7 @@ def dependency_status():
     result = {name: bool(shutil.which(name)) for name in checks}
     result["ani-cli"] = cli_executable_exists(ANI_CLI)
     result["anipy-cli"] = cli_executable_exists(ANIPY_CLI)
+    result["animdl"] = cli_executable_exists(ANIMDL)
     return result
 
 
@@ -248,6 +250,22 @@ def installed_anipy_cli_version():
     return version or "Unavailable"
 
 
+@lru_cache(maxsize=1)
+def installed_animdl_version():
+    try:
+        completed = subprocess.run(
+            [ANIMDL, "--version"],
+            check=True,
+            capture_output=True,
+            text=True,
+            timeout=6,
+        )
+    except (OSError, subprocess.SubprocessError):
+        return "Unavailable"
+    version = str(completed.stdout or completed.stderr or "").strip()
+    return version or "Unavailable"
+
+
 class Handler(BaseHTTPRequestHandler):
     server_version = "AniCliWeb/1.0"
     remote_session_cookie_name = "ani_cli_web_session"
@@ -629,6 +647,7 @@ class Handler(BaseHTTPRequestHandler):
                         "version": VERSION,
                         "ani_cli_version": installed_ani_cli_version(),
                         "anipy_cli_version": installed_anipy_cli_version(),
+                        "animdl_version": installed_animdl_version(),
                     }
                 )
             elif parsed.path == "/api/changelog":