revert: remove fork-only changes from release sync

Revert payment/wechat, sora/claude-max cleanup, fork-only migrations,
and cosmetic changes that were brought in by the release sync commit.
Keep only channel-monitor related improvements:
- PublicSettingsInjectionPayload named struct with drift test
- ChannelMonitorRunner graceful shutdown in wire
- image_output_price in SupportedModelChip
- Simplified buildSelfNavItems in AppSidebar
- Gateway WARN logs for 503 branches

backend/internal/repository/gateway_cache.go

@@ -9,9 +9,7 @@ import (
 	"github.com/redis/go-redis/v9"
 )
 
-const (
-	stickySessionPrefix = "sticky_session:"
-)
+const stickySessionPrefix = "sticky_session:"
 
 type gatewayCache struct {
 	rdb *redis.Client
@@ -43,6 +41,12 @@ func (c *gatewayCache) RefreshSessionTTL(ctx context.Context, groupID int64, ses
 }
 
 // DeleteSessionAccountID 删除粘性会话与账号的绑定关系。
+// 当检测到绑定的账号不可用（如状态错误、禁用、不可调度等）时调用，
+// 以便下次请求能够重新选择可用账号。
+//
+// DeleteSessionAccountID removes the sticky session binding for the given session.
+// Called when the bound account becomes unavailable (e.g., error status, disabled,
+// or unschedulable), allowing subsequent requests to select a new available account.
 func (c *gatewayCache) DeleteSessionAccountID(ctx context.Context, groupID int64, sessionHash string) error {
 	key := buildSessionKey(groupID, sessionHash)
 	return c.rdb.Del(ctx, key).Err()