IAV-255/feat(agent): Add active flag to AgentLanguage entity

Description

This MR adds an active boolean field to the AgentLanguage entity to enable activation and deactivation of agent languages.

Changes

• Added active field to AgentLanguage entity
• Field allows tracking whether a language is currently active for an agent

Technical Details

• Field type: boolean
• Database column: active
• No constraints applied (nullable by default)

Testing

• Entity mapping verified
• Database tested
• No breaking changes to existing functionality