feat(#82): implement Personality Module

- Add Personality model to Prisma schema with FormalityLevel enum
- Create migration and seed with 6 default personalities
- Implement CRUD API with TDD approach (97.67% coverage)
  * PersonalitiesService: findAll, findOne, findDefault, create, update, remove
  * PersonalitiesController: REST endpoints with auth guards
  * Comprehensive test coverage (21 passing tests)
- Add Personality types to shared package
- Create frontend components:
  * PersonalitySelector: dropdown for choosing personality
  * PersonalityPreview: preview personality style and system prompt
  * PersonalityForm: create/edit personalities with validation
  * Settings page: manage personalities with CRUD operations
- Integrate with Ollama API:
  * Support personalityId in chat endpoint
  * Auto-inject system prompt from personality
  * Fall back to default personality if not specified
- API client for frontend personality management

All tests passing with 97.67% backend coverage (exceeds 85% requirement)

apps/web/src/components/domains/DomainSelector.test.tsx

@@ -0,0 +1,127 @@
+import { describe, it, expect, vi } from "vitest";
+import { render, screen } from "@testing-library/react";
+import userEvent from "@testing-library/user-event";
+import { DomainSelector } from "./DomainSelector";
+import type { Domain } from "@mosaic/shared";
+
+describe("DomainSelector", () => {
+  const mockDomains: Domain[] = [
+    {
+      id: "domain-1",
+      workspaceId: "workspace-1",
+      name: "Work",
+      slug: "work",
+      description: "Work-related tasks",
+      color: "#3B82F6",
+      icon: "💼",
+      sortOrder: 0,
+      metadata: {},
+      createdAt: new Date("2026-01-28"),
+      updatedAt: new Date("2026-01-28"),
+    },
+    {
+      id: "domain-2",
+      workspaceId: "workspace-1",
+      name: "Personal",
+      slug: "personal",
+      description: null,
+      color: "#10B981",
+      icon: null,
+      sortOrder: 1,
+      metadata: {},
+      createdAt: new Date("2026-01-28"),
+      updatedAt: new Date("2026-01-28"),
+    },
+  ];
+
+  it("should render with default placeholder", () => {
+    const onChange = vi.fn();
+    render(
+      <DomainSelector domains={mockDomains} value={null} onChange={onChange} />
+    );
+    expect(screen.getByText("Select a domain")).toBeInTheDocument();
+  });
+
+  it("should render with custom placeholder", () => {
+    const onChange = vi.fn();
+    render(
+      <DomainSelector
+        domains={mockDomains}
+        value={null}
+        onChange={onChange}
+        placeholder="Choose domain"
+      />
+    );
+    expect(screen.getByText("Choose domain")).toBeInTheDocument();
+  });
+
+  it("should render all domains as options", () => {
+    const onChange = vi.fn();
+    render(
+      <DomainSelector domains={mockDomains} value={null} onChange={onChange} />
+    );
+    expect(screen.getByText("💼 Work")).toBeInTheDocument();
+    expect(screen.getByText("Personal")).toBeInTheDocument();
+  });
+
+  it("should call onChange when selection changes", async () => {
+    const user = userEvent.setup();
+    const onChange = vi.fn();
+    
+    render(
+      <DomainSelector domains={mockDomains} value={null} onChange={onChange} />
+    );
+
+    const select = screen.getByRole("combobox");
+    await user.selectOptions(select, "domain-1");
+
+    expect(onChange).toHaveBeenCalledWith("domain-1");
+  });
+
+  it("should call onChange with null when cleared", async () => {
+    const user = userEvent.setup();
+    const onChange = vi.fn();
+    
+    render(
+      <DomainSelector
+        domains={mockDomains}
+        value="domain-1"
+        onChange={onChange}
+      />
+    );
+
+    const select = screen.getByRole("combobox");
+    await user.selectOptions(select, "");
+
+    expect(onChange).toHaveBeenCalledWith(null);
+  });
+
+  it("should show selected value", () => {
+    const onChange = vi.fn();
+    render(
+      <DomainSelector
+        domains={mockDomains}
+        value="domain-1"
+        onChange={onChange}
+      />
+    );
+
+    const select = screen.getByRole("combobox") as HTMLSelectElement;
+    expect(select.value).toBe("domain-1");
+  });
+
+  it("should apply custom className", () => {
+    const onChange = vi.fn();
+    render(
+      <DomainSelector
+        domains={mockDomains}
+        value={null}
+        onChange={onChange}
+        className="custom-class"
+      />
+    );
+
+    const select = screen.getByRole("combobox");
+    expect(select.className).toContain("custom-class");
+  });
+});