✨ feat: Add model icon support across backend and UI; prefer model icon over vendor; add icon column in Models table
Backend:
- Model: Add `icon` field to `model.Model` (gorm: varchar(128)); auto-migrated via GORM.
- Pricing API: Extend `model.Pricing` with `icon` and populate from model meta in `GetPricing()`.
Frontend:
- EditModelModal: Add `icon` input (with @lobehub/icons helper link); wire into init/load/submit flows.
- ModelHeader / PricingCardView: Prefer rendering `model.icon`; fallback to `vendor_icon`; final fallback to initials avatar.
- Models table: Add leading “Icon” column, rendering `model.icon` or `vendor` icon via `getLobeHubIcon`.
Notes:
- Backward-compatible. Existing data without `icon` remain unaffected.
- No manual SQL needed; column is added by AutoMigrate.
Affected files:
- model/model_meta.go
- model/pricing.go
- web/src/components/table/models/modals/EditModelModal.jsx
- web/src/components/table/model-pricing/modal/components/ModelHeader.jsx
- web/src/components/table/model-pricing/view/card/PricingCardView.jsx
- web/src/components/table/models/ModelsColumnDefs.js
