refactor: optimize agent list payload and improve multimodal detection logic

[eviaaaaa]

Description

This PR focuses on API performance optimization and refining the model capability detection logic in the Agent/Canvas module.

1. Performance Optimization (Backend)

• Changes: Removed cls.model.dsl from query fields in UserCanvasService.get_by_tenant_ids.
• Reasoning: The dsl object is large and unnecessary for the Agent list view. Excluding it reduces the payload size of the /v1/canvas/list API, leading to faster serialization and reduced network latency.
• Consistency: Full DSL data remains accessible via the individual /v1/canvas/get/<id> endpoint used in the detail view.

2. Multimodal Detection Refinement (Frontend)

• Changes: Replaced model_type === LlmModelType.Image2text with tags?.includes('IMAGE2TEXT').
• Reasoning: In RAGFlow, model_type defines the primary role of a model (e.g., chat). However, many advanced Chat models are also vision-capable. Since model_type is a single-value field, it cannot represent these multiple capabilities.
• Solution: Utilizing the tags field (which supports multiple attributes) to check for IMAGE2TEXT ensures that models like gpt-5.2-pro correctly display multimodal input options.

Type of Change

• Bug fix (logic correction for multimodal detection)
• Optimization (performance improvement for list API)

Main Changes

• api/db/services/canvas_service.py: Optimized DB query by excluding heavy DSL fields.
• web/src/pages/agent/form/agent-form/index.tsx: Enhanced capability detection using the tags system.

Verification

• Verified Agent list loads faster with reduced response payload.
• Confirmed that chat models with the IMAGE2TEXT tag now correctly enable the multimodal input UI.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 44.46%. Comparing base (23bdf25) to head (ffa09cf).
⚠️ Report is 11 commits behind head on main.

Additional details and impacted files

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  Coverage   44.46%   44.46%           
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  Files          43       43           
  Lines        9266     9266           
  Branches      107      107           
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  Hits         4120     4120           
  Misses       5127     5127           
  Partials       19       19           

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