Add admin reset-password command

Features:
- Add admin reset-password command to reset user passwords
- Support SQLite, PostgreSQL, and MySQL databases
- Use scrypt hashing compatible with CodiMD
- Update README with reset-password usage examples

cli_anything/codimd/core/db.py

@@ -9,6 +9,45 @@ from typing import List, Dict, Any, Optional
 from pathlib import Path
 
 
+class PasswordHasher:
+    """Password hashing compatible with CodiMD (scrypt-kdf)."""
+
+    @staticmethod
+    def hash_password(password: str) -> str:
+        """Hash password using scrypt (compatible with CodiMD).
+
+        CodiMD uses scrypt-kdf with default parameters (N=16384, r=8, p=1).
+        Returns hex-encoded hash that CodiMD can verify.
+        """
+        try:
+            import hashlib
+            import scrypt
+            import os
+            # Generate random salt (16 bytes)
+            salt = os.urandom(16)
+            # Scrypt parameters matching CodiMD defaults
+            N = 16384
+            r = 8
+            p = 1
+            # Derive key (64 bytes output)
+            derived_key = scrypt.hash(
+                password.encode(),
+                salt,
+                N,
+                r,
+                p,
+                64  # output length in bytes
+            )
+            # Return hex-encoded salt + hash (CodiMD format)
+            return salt.hex() + derived_key.hex()
+        except ImportError:
+            raise ImportError(
+                "scrypt required for password operations. "
+                "Install with: pip install scrypt\n"
+                "Or install with: pip install cli-anything-codimd[admin]"
+            )
+
+
 class CodiMDDatabase:
     """Direct database access for CodiMD."""
 
@@ -148,3 +187,147 @@ class CodiMDDatabase:
         notes = [dict(row) for row in cursor.fetchall()]
         conn.close()
         return notes
+
+    @staticmethod
+    def reset_password_sqlite(db_path: str, email: str, new_password: str) -> bool:
+        """Reset user password in SQLite database."""
+        try:
+            import sqlite3
+        except ImportError:
+            raise ImportError("sqlite3 required for SQLite access")
+
+        # Hash the new password
+        hashed_password = PasswordHasher.hash_password(new_password)
+
+        conn = sqlite3.connect(db_path)
+        cursor = conn.cursor()
+
+        # Check if user exists by email
+        cursor.execute("SELECT id, email FROM Users WHERE email = ?", (email,))
+        user = cursor.fetchone()
+
+        if not user:
+            conn.close()
+            raise ValueError(f"User not found: {email}")
+
+        user_id, user_email = user
+
+        # Update password
+        cursor.execute(
+            'UPDATE Users SET password = ? WHERE email = ?',
+            (hashed_password, email)
+        )
+
+        conn.commit()
+        conn.close()
+        return True
+
+    @staticmethod
+    def reset_password_sqlite_by_id(db_path: str, user_id: str, new_password: str) -> bool:
+        """Reset user password in SQLite database by user ID."""
+        try:
+            import sqlite3
+        except ImportError:
+            raise ImportError("sqlite3 required for SQLite access")
+
+        # Hash the new password
+        hashed_password = PasswordHasher.hash_password(new_password)
+
+        conn = sqlite3.connect(db_path)
+        cursor = conn.cursor()
+
+        # Check if user exists
+        cursor.execute("SELECT id, email FROM Users WHERE id = ?", (user_id,))
+        user = cursor.fetchone()
+
+        if not user:
+            conn.close()
+            raise ValueError(f"User not found: {user_id}")
+
+        # Update password
+        cursor.execute(
+            'UPDATE Users SET password = ? WHERE id = ?',
+            (hashed_password, user_id)
+        )
+
+        conn.commit()
+        conn.close()
+        return True
+
+    @staticmethod
+    def reset_password_postgresql(host: str, database: str, user: str, password: str,
+                                  port: int, target_email: str, new_password: str) -> bool:
+        """Reset user password in PostgreSQL database."""
+        try:
+            import psycopg2
+        except ImportError:
+            raise ImportError("psycopg2 required for PostgreSQL access")
+
+        # Hash the new password
+        hashed_password = PasswordHasher.hash_password(new_password)
+
+        conn = psycopg2.connect(
+            host=host,
+            database=database,
+            user=user,
+            password=password,
+            port=port
+        )
+        cursor = conn.cursor()
+
+        # Check if user exists
+        cursor.execute('SELECT id, email FROM "Users" WHERE email = %s', (target_email,))
+        row = cursor.fetchone()
+
+        if not row:
+            conn.close()
+            raise ValueError(f"User not found: {target_email}")
+
+        # Update password
+        cursor.execute(
+            'UPDATE "Users" SET password = %s WHERE email = %s',
+            (hashed_password, target_email)
+        )
+
+        conn.commit()
+        conn.close()
+        return True
+
+    @staticmethod
+    def reset_password_mysql(host: str, database: str, user: str, password: str,
+                            port: int, target_email: str, new_password: str) -> bool:
+        """Reset user password in MySQL database."""
+        try:
+            import mysql.connector
+        except ImportError:
+            raise ImportError("mysql-connector-python required for MySQL access")
+
+        # Hash the new password
+        hashed_password = PasswordHasher.hash_password(new_password)
+
+        conn = mysql.connector.connect(
+            host=host,
+            database=database,
+            user=user,
+            password=password,
+            port=port
+        )
+        cursor = conn.cursor()
+
+        # Check if user exists
+        cursor.execute('SELECT id, email FROM Users WHERE email = %s', (target_email,))
+        row = cursor.fetchone()
+
+        if not row:
+            conn.close()
+            raise ValueError(f"User not found: {target_email}")
+
+        # Update password
+        cursor.execute(
+            'UPDATE Users SET password = %s WHERE email = %s',
+            (hashed_password, target_email)
+        )
+
+        conn.commit()
+        conn.close()
+        return True