Migrate from file-based configs to database with per-IP site configuration

Major architectural changes:
   - Replace YAML config files with database-stored ScanConfig model
   - Remove CIDR block support in favor of individual IP addresses per site
   - Each IP now has its own expected_ping, expected_tcp_ports, expected_udp_ports
   - AlertRule now uses config_id FK instead of config_file string

   API changes:
   - POST /api/scans now requires config_id instead of config_file
   - Alert rules API uses config_id with validation
   - All config dropdowns fetch from /api/configs dynamically

   Template updates:
   - scans.html, dashboard.html, alert_rules.html load configs via API
   - Display format: Config Title (X sites) in dropdowns
   - Removed Jinja2 config_files loops

   Migrations:
   - 008: Expand CIDRs to individual IPs with per-IP port configs
   - 009: Remove CIDR-related columns
   - 010: Add config_id to alert_rules, remove config_file

app/migrations/versions/010_alert_rules_config_id.py

@@ -0,0 +1,53 @@
+"""Add config_id to alert_rules table
+
+Revision ID: 010
+Revises: 009
+Create Date: 2025-11-19
+
+This migration adds config_id foreign key to alert_rules table to replace
+the config_file column, completing the migration from file-based to
+database-based configurations.
+"""
+from alembic import op
+import sqlalchemy as sa
+
+
+# revision identifiers, used by Alembic
+revision = '010'
+down_revision = '009'
+branch_labels = None
+depends_on = None
+
+
+def upgrade():
+    """
+    Add config_id to alert_rules table and remove config_file.
+    """
+
+    with op.batch_alter_table('alert_rules', schema=None) as batch_op:
+        # Add config_id column with foreign key
+        batch_op.add_column(sa.Column('config_id', sa.Integer(), nullable=True, comment='FK to scan_configs table'))
+        batch_op.create_index('ix_alert_rules_config_id', ['config_id'], unique=False)
+        batch_op.create_foreign_key('fk_alert_rules_config_id', 'scan_configs', ['config_id'], ['id'])
+
+        # Remove the old config_file column
+        batch_op.drop_column('config_file')
+
+    print("✓ Migration complete: AlertRule now uses config_id")
+    print("  - Added config_id foreign key to alert_rules table")
+    print("  - Removed deprecated config_file column")
+
+
+def downgrade():
+    """Remove config_id and restore config_file on alert_rules."""
+
+    with op.batch_alter_table('alert_rules', schema=None) as batch_op:
+        # Remove foreign key and config_id column
+        batch_op.drop_constraint('fk_alert_rules_config_id', type_='foreignkey')
+        batch_op.drop_index('ix_alert_rules_config_id')
+        batch_op.drop_column('config_id')
+
+        # Restore config_file column
+        batch_op.add_column(sa.Column('config_file', sa.String(255), nullable=True, comment='Optional: specific config file this rule applies to'))
+
+    print("✓ Downgrade complete: AlertRule config_id removed, config_file restored")