feat: implement Story 1.1 — create and view diagrams

Add diagram/project DB schema, CRUD API, dashboard pages with grid/card/
empty state, create dialog with type selector, editor placeholder, and
26 schema validation tests. Includes code review fixes: soft-delete
filter on GET /:id, error handling, keyboard accessibility, type-safe
API response types, and error states on pages.

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

packages/api/tests/diagram/diagram-schema.test.ts

@@ -0,0 +1,134 @@
+import { describe, it, expect } from "vitest";
+
+import { createDiagramSchema } from "../../src/modules/diagram/router";
+
+describe("createDiagramSchema", () => {
+  describe("title field", () => {
+    it("should accept a valid title", () => {
+      const result = createDiagramSchema.safeParse({
+        title: "My Diagram",
+        type: "flowchart",
+      });
+      expect(result.success).toBe(true);
+    });
+
+    it("should reject empty title", () => {
+      const result = createDiagramSchema.safeParse({
+        title: "",
+        type: "flowchart",
+      });
+      expect(result.success).toBe(false);
+    });
+
+    it("should reject title over 255 characters", () => {
+      const result = createDiagramSchema.safeParse({
+        title: "a".repeat(256),
+        type: "flowchart",
+      });
+      expect(result.success).toBe(false);
+    });
+
+    it("should accept title at max length (255)", () => {
+      const result = createDiagramSchema.safeParse({
+        title: "a".repeat(255),
+        type: "flowchart",
+      });
+      expect(result.success).toBe(true);
+    });
+
+    it("should reject missing title", () => {
+      const result = createDiagramSchema.safeParse({
+        type: "flowchart",
+      });
+      expect(result.success).toBe(false);
+    });
+  });
+
+  describe("type field", () => {
+    const validTypes = [
+      "bpmn",
+      "er",
+      "orgchart",
+      "architecture",
+      "sequence",
+      "flowchart",
+    ] as const;
+
+    validTypes.forEach((type) => {
+      it(`should accept type '${type}'`, () => {
+        const result = createDiagramSchema.safeParse({
+          title: "Test",
+          type,
+        });
+        expect(result.success).toBe(true);
+      });
+    });
+
+    it("should reject invalid type", () => {
+      const result = createDiagramSchema.safeParse({
+        title: "Test",
+        type: "invalid",
+      });
+      expect(result.success).toBe(false);
+    });
+
+    it("should reject missing type", () => {
+      const result = createDiagramSchema.safeParse({
+        title: "Test",
+      });
+      expect(result.success).toBe(false);
+    });
+  });
+
+  describe("projectId field", () => {
+    it("should accept optional projectId", () => {
+      const result = createDiagramSchema.safeParse({
+        title: "Test",
+        type: "bpmn",
+        projectId: "proj-123",
+      });
+      expect(result.success).toBe(true);
+      if (result.success) {
+        expect(result.data.projectId).toBe("proj-123");
+      }
+    });
+
+    it("should accept missing projectId", () => {
+      const result = createDiagramSchema.safeParse({
+        title: "Test",
+        type: "bpmn",
+      });
+      expect(result.success).toBe(true);
+      if (result.success) {
+        expect(result.data.projectId).toBeUndefined();
+      }
+    });
+  });
+
+  describe("complete valid input", () => {
+    it("should parse valid input correctly", () => {
+      const input = {
+        title: "System Architecture",
+        type: "architecture" as const,
+        projectId: "proj-abc",
+      };
+      const result = createDiagramSchema.safeParse(input);
+      expect(result.success).toBe(true);
+      if (result.success) {
+        expect(result.data).toEqual(input);
+      }
+    });
+
+    it("should strip unknown fields", () => {
+      const result = createDiagramSchema.safeParse({
+        title: "Test",
+        type: "flowchart",
+        unknownField: "should be stripped",
+      });
+      expect(result.success).toBe(true);
+      if (result.success) {
+        expect(result.data).not.toHaveProperty("unknownField");
+      }
+    });
+  });
+});