Add Alembic migration system for database schema versioning

- Introduced `alembic.ini` for Alembic configuration, enabling structured database migrations.
- Created `database/migrations/env.py` to manage migration environment and database URL retrieval.
- Added migration script template `database/migrations/script.py.mako` for generating migration scripts.
- Updated `.gitignore` to exclude migration versions from version control.
- Enhanced `setup.md` documentation to include details on the migration system and commands for managing migrations.

database/migrations/README

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+Generic single-database configuration.

database/migrations/env.py

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+"""
+Alembic Environment Configuration for Crypto Trading Bot Platform
+"""
+
+import os
+import sys
+from logging.config import fileConfig
+from pathlib import Path
+
+from sqlalchemy import engine_from_config
+from sqlalchemy import pool
+
+from alembic import context
+
+# Add project root to path for imports
+project_root = Path(__file__).parent.parent.parent
+sys.path.insert(0, str(project_root))
+
+# Load environment variables from .env file if it exists
+try:
+    from dotenv import load_dotenv
+    env_file = project_root / '.env'
+    if env_file.exists():
+        load_dotenv(env_file)
+except ImportError:
+    # dotenv not available, proceed without it
+    pass
+
+# Import our models and database configuration
+from database.models import Base
+from database.connection import DatabaseConfig
+
+# this is the Alembic Config object, which provides
+# access to the values within the .ini file in use.
+config = context.config
+
+# Interpret the config file for Python logging.
+# This line sets up loggers basically.
+if config.config_file_name is not None:
+    fileConfig(config.config_file_name)
+
+# add your model's MetaData object here
+# for 'autogenerate' support
+target_metadata = Base.metadata
+
+# other values from the config, defined by the needs of env.py,
+# can be acquired:
+# my_important_option = config.get_main_option("my_important_option")
+# ... etc.
+
+
+def get_database_url():
+    """Get database URL from environment variables"""
+    # Use DATABASE_URL if set, otherwise construct from individual components
+    url = os.getenv('DATABASE_URL')
+    if url:
+        return url
+    
+    # Fallback to constructing URL from components
+    user = os.getenv('POSTGRES_USER', 'dashboard')
+    password = os.getenv('POSTGRES_PASSWORD', '')
+    host = os.getenv('POSTGRES_HOST', 'localhost')
+    port = os.getenv('POSTGRES_PORT', '5434')
+    database = os.getenv('POSTGRES_DB', 'dashboard')
+    
+    return f"postgresql://{user}:{password}@{host}:{port}/{database}"
+
+
+def run_migrations_offline() -> None:
+    """Run migrations in 'offline' mode.
+
+    This configures the context with just a URL
+    and not an Engine, though an Engine is acceptable
+    here as well.  By skipping the Engine creation
+    we don't even need a DBAPI to be available.
+
+    Calls to context.execute() here emit the given string to the
+    script output.
+
+    """
+    url = get_database_url()
+    context.configure(
+        url=url,
+        target_metadata=target_metadata,
+        literal_binds=True,
+        dialect_opts={"paramstyle": "named"},
+        compare_type=True,
+        compare_server_default=True,
+        render_as_batch=False,  # PostgreSQL supports transactional DDL
+    )
+
+    with context.begin_transaction():
+        context.run_migrations()
+
+
+def run_migrations_online() -> None:
+    """Run migrations in 'online' mode.
+
+    In this scenario we need to create an Engine
+    and associate a connection with the context.
+
+    """
+    # Override the sqlalchemy.url in the config with our environment-based URL
+    config.set_main_option("sqlalchemy.url", get_database_url())
+    
+    # Create engine with our database configuration
+    db_config = DatabaseConfig()
+    engine_config = config.get_section(config.config_ini_section)
+    engine_config.update(db_config.get_engine_kwargs())
+    
+    connectable = engine_from_config(
+        engine_config,
+        prefix="sqlalchemy.",
+        poolclass=pool.NullPool,  # Use NullPool for migrations to avoid connection issues
+    )
+
+    with connectable.connect() as connection:
+        context.configure(
+            connection=connection,
+            target_metadata=target_metadata,
+            compare_type=True,
+            compare_server_default=True,
+            render_as_batch=False,  # PostgreSQL supports transactional DDL
+            transaction_per_migration=True,  # Each migration in its own transaction
+        )
+
+        with context.begin_transaction():
+            context.run_migrations()
+
+
+if context.is_offline_mode():
+    run_migrations_offline()
+else:
+    run_migrations_online()

database/migrations/script.py.mako

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+"""${message}
+
+Revision ID: ${up_revision}
+Revises: ${down_revision | comma,n}
+Create Date: ${create_date}
+
+"""
+from typing import Sequence, Union
+
+from alembic import op
+import sqlalchemy as sa
+${imports if imports else ""}
+
+# revision identifiers, used by Alembic.
+revision: str = ${repr(up_revision)}
+down_revision: Union[str, None] = ${repr(down_revision)}
+branch_labels: Union[str, Sequence[str], None] = ${repr(branch_labels)}
+depends_on: Union[str, Sequence[str], None] = ${repr(depends_on)}
+
+
+def upgrade() -> None:
+    """Upgrade schema."""
+    ${upgrades if upgrades else "pass"}
+
+
+def downgrade() -> None:
+    """Downgrade schema."""
+    ${downgrades if downgrades else "pass"}