在 SQL 查询中使用 CASE WHEN > 0 回退策略，让渠道定价的扩展比率
(cache_ratio, cache_creation_ratio, image_ratio, audio_ratio,
audio_completion_ratio) 在未设置时自动回退到全局默认值，
而不是像 COALESCE 那样被零值拦截。同时更新 GROUP BY 子句包含所有
新选择的列，确保 MySQL 兼容。
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
This PR fixes three issues:
1. Token bound_channel_id not updating: Add bound field to Update() method
2. Channel pricing quota_type detection: Use QuotaTypeByCall constant instead of magic number 1
3. Log display for ratio-based pricing: Set ModelPrice=-1 for ratio-based pricing
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
The previous implementation only did INSERT without handling conflicts.
Now uses GORM's OnConflict clause to properly update existing records
when (model_name, channel_id) unique constraint is violated.
On conflict updates: quota_type, model_ratio, completion_ratio,
model_price, tag_ids, updated_time
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Add new model to support per-channel pricing for models,
allowing the same model to have different prices across
different channels.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
fengsilin