Add a new /api/user/channels endpoint that returns only enabled channels
with non-sensitive fields (id, name, type, remark) for token channel binding.
Update EditTokenModal to use this endpoint and display remark instead of ID
in the channel dropdown.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Add new route groups for channel pricing and pricing tag management
with AdminAuth middleware.

Routes added:
- /api/channel_pricing/*: CRUD operations for channel pricing
- /api/pricing_tag/*: CRUD operations for pricing tags

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>