feat: Click CLI wrapper for cantaloupe export

- cantaloupe/ package with click CLI (python -m cantaloupe export)
- export command: --output, --headless/--visible, --scheduled, --email, --password
- configure command: saves credentials to ~/.cantaloupe.env (600 perms)
- cantaloupe/config.py: credential loading from env vars + env file
- Updated src/auth.py _get_credentials() to also check ~/.cantaloupe.env
- File size, row count (openpyxl), and elapsed time reporting
- 39 new CLI/config tests + 4 updated auth tests; 86/86 pass

cantaloupe/config.py

@@ -0,0 +1,93 @@
+"""
+Credential management for cantaloupe CLI.
+
+Reads credentials from:
+  1. CANTALOUPE_EMAIL / CANTALOUPE_PASSWORD environment variables
+  2. ~/.cantaloupe.env file (key=value format)
+
+Saves credentials to ~/.cantaloupe.env with restrictive permissions (600).
+"""
+
+import os
+from pathlib import Path
+
+ENV_FILE = Path.home() / ".cantaloupe.env"
+ENV_EMAIL_KEY = "CANTALOUPE_EMAIL"
+ENV_PASSWORD_KEY = "CANTALOUPE_PASSWORD"
+
+
+def load_credentials() -> tuple[str, str]:
+    """Load credentials from env vars or ~/.cantaloupe.env.
+
+    Priority: environment variables override the env file.
+    Returns (email, password) — either or both may be empty strings.
+    """
+    email = os.environ.get(ENV_EMAIL_KEY, "")
+    password = os.environ.get(ENV_PASSWORD_KEY, "")
+
+    # If both are set via env, use them
+    if email and password:
+        return email, password
+
+    # Check the env file
+    if ENV_FILE.exists():
+        for line in ENV_FILE.read_text().splitlines():
+            line = line.strip()
+            if not line or line.startswith("#") or "=" not in line:
+                continue
+            key, _, value = line.partition("=")
+            key = key.strip()
+            value = value.strip().strip('"').strip("'")
+            if key == ENV_EMAIL_KEY and not email:
+                email = value
+            elif key == ENV_PASSWORD_KEY and not password:
+                password = value
+
+    return email, password
+
+
+def save_credentials(email: str, password: str) -> Path:
+    """Save credentials to ~/.cantaloupe.env.
+
+    Updates the email/password lines in-place, preserving any other
+    configuration lines that may be present. Sets file permissions to 600.
+
+    Returns the path to the env file.
+    """
+    ENV_FILE.parent.mkdir(parents=True, exist_ok=True)
+
+    # Read existing lines, filtering out old credential entries
+    lines: list[str] = []
+    if ENV_FILE.exists():
+        for line in ENV_FILE.read_text().splitlines():
+            stripped = line.strip()
+            if stripped.startswith(f"{ENV_EMAIL_KEY}=") or stripped.startswith(
+                f"{ENV_PASSWORD_KEY}="
+            ):
+                continue
+            lines.append(line)
+
+    # Append new credentials
+    lines.append(f"{ENV_EMAIL_KEY}={email}")
+    lines.append(f"{ENV_PASSWORD_KEY}={password}")
+
+    ENV_FILE.write_text("\n".join(lines) + "\n")
+    ENV_FILE.chmod(0o600)
+
+    return ENV_FILE
+
+
+def prompt_credentials() -> tuple[str, str]:
+    """Prompt interactively for credentials.
+
+    Uses input() for email and getpass() for password.
+    Returns (email, password) — empty strings if cancelled.
+    """
+    try:
+        import getpass
+
+        email = input("Cantaloupe email: ").strip()
+        password = getpass.getpass("Cantaloupe password: ")
+        return email, password
+    except (EOFError, KeyboardInterrupt):
+        return "", ""