feat(server): add brand kit management and project binding

Add a brand kit domain with memory and postgres stores, a BrandKitService
for CRUD and resolution, and REST endpoints to list, upsert, and delete
brand kits. Projects can bind a brand kit whose resolved context and
reference images feed into the agent's long-term memory and design prompts.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

server/internal/logic/upsert_brand_kit_logic.go

@@ -0,0 +1,35 @@
+// Code scaffolded by goctl. Safe to edit.
+// goctl 1.10.1
+
+package logic
+
+import (
+	"context"
+
+	"img_infinite_canvas/internal/svc"
+	"img_infinite_canvas/internal/types"
+
+	"github.com/zeromicro/go-zero/core/logx"
+)
+
+type UpsertBrandKitLogic struct {
+	logx.Logger
+	ctx    context.Context
+	svcCtx *svc.ServiceContext
+}
+
+func NewUpsertBrandKitLogic(ctx context.Context, svcCtx *svc.ServiceContext) *UpsertBrandKitLogic {
+	return &UpsertBrandKitLogic{
+		Logger: logx.WithContext(ctx),
+		ctx:    ctx,
+		svcCtx: svcCtx,
+	}
+}
+
+func (l *UpsertBrandKitLogic) UpsertBrandKit(req *types.UpsertBrandKitRequest) (resp *types.BrandKitResponse, err error) {
+	kit, err := l.svcCtx.BrandKitService.Upsert(l.ctx, req.Id, req.Document, req.IsDefault)
+	if err != nil {
+		return nil, err
+	}
+	return &types.BrandKitResponse{BrandKit: toAPIBrandKit(kit)}, nil
+}