Refactor Template Agents Architecture: Add Template Agent Support, Improve DB Handling, and Unify UI Sidebar

[Ashad001]

This pull request introduces major improvements to the architecture and UI alignment:

Template Agent Support

• Integrated support for template agents, replacing custom_agents_router with templates_router.
• Agent discovery logic updated to categorize standard, custom, and template agents uniformly.
• chat_with_agent function refactored to support database-driven template agent execution.

Improved Database Handling

• Switched agent listing to use the AgentTemplate model.
• Enhanced error logging and validation logic for agent availability and retrieval.

Timeout + Logging Optimization

• Increased request timeout to 120s for longer tasks.
• Removed redundant logs to clean up console output and boost performance.

Data + Dependency Updates

• Added polars to requirements.txt for faster dataframe ops (replacing some pandas/numpy usage).
• Updated property data and added visualization assets for improved insights.

Script Refactor

• populate_agent_templates.py now populates AgentTemplate (not CustomAgent) and includes icons + new prompt formats using polars.

UI Sidebar Shift

• The UI now reflects a unified agent system: template agents are accessible directly via the main sidebar, removing the need for a separate custom agents sidebar. This streamlines the user experience and aligns with standard agent access.