Initial commit: img-infinite-canvas AI design workbench MVP

Moteva-style AI design workbench replica. Home prompt creates a project;
the project page provides an infinite canvas with node drag, zoom/pan,
a design chat panel, history replay, image asset upload, and project
save/regenerate.

- Backend: go-zero, DDD layering, sqlc/pgx, optional PostgreSQL; memory
  or Redis cache; asynq job queue; MinIO/S3/R2/OSS object storage;
  sky-valley/pi agent runtime adapter.
- Frontend: Next.js App Router + Vite artifact build, TypeScript, i18n,
  shadcn/ui components, auth (OTP/Turnstile/Google/WeChat).
- Deploy: Docker Compose and k3s manifests.

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

server/internal/application/deterministic_agent.go

@@ -0,0 +1,52 @@
+package application
+
+import (
+	"context"
+	"fmt"
+
+	"img_infinite_canvas/internal/domain/design"
+)
+
+type DeterministicAgent struct{}
+
+func NewDeterministicAgent() *DeterministicAgent {
+	return &DeterministicAgent{}
+}
+
+func (a *DeterministicAgent) Plan(ctx context.Context, req design.AgentRequest) (design.AgentPlan, error) {
+	if err := ctx.Err(); err != nil {
+		return design.AgentPlan{}, err
+	}
+
+	offset := len(req.Project.Nodes)
+	nodes := composeBoard(req.Prompt, offset)
+	return design.AgentPlan{
+		Message: design.Message{
+			ID:      newID(),
+			Role:    "assistant",
+			Type:    "assistant",
+			Title:   "设计任务完成",
+			Content: synthesizeResponse(req.Prompt, req.Mode),
+		},
+		GeneratedNodes: nodes,
+		Connections:    nil,
+	}, nil
+}
+
+func (a *DeterministicAgent) Replay(ctx context.Context, project design.Project) (design.AgentReplay, error) {
+	if err := ctx.Err(); err != nil {
+		return design.AgentReplay{}, err
+	}
+
+	return design.AgentReplay{
+		ProjectID: project.ID,
+		Messages:  append([]design.Message(nil), project.Messages...),
+	}, nil
+}
+
+func synthesizeResponse(prompt string, mode string) string {
+	if mode == "" {
+		mode = "design"
+	}
+	return fmt.Sprintf("已按「%s」生成一组 %s 画布：官网首页、色彩卡片、移动端页面和详情页已放到无限画布中，可继续微调、扩展或上传参考图。视频生成暂未接入，当前聚焦图片、页面与品牌视觉。", prompt, mode)
+}