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.tsx

@@ -0,0 +1,38 @@
+"use client";
+
+import type { Domain } from "@mosaic/shared";
+
+interface DomainSelectorProps {
+  domains: Domain[];
+  value: string | null;
+  onChange: (domainId: string | null) => void;
+  placeholder?: string;
+  className?: string;
+}
+
+export function DomainSelector({
+  domains,
+  value,
+  onChange,
+  placeholder = "Select a domain",
+  className = "",
+}: DomainSelectorProps): JSX.Element {
+  return (
+    <select
+      value={value ?? ""}
+      onChange={(e: React.ChangeEvent<HTMLSelectElement>) =>
+        onChange(e.target.value || null)
+      }
+      className={`border rounded px-3 py-2 ${className}`}
+      aria-label="Domain selector"
+    >
+      <option value="">{placeholder}</option>
+      {domains.map((domain) => (
+        <option key={domain.id} value={domain.id}>
+          {domain.icon ? `${domain.icon} ` : ""}
+          {domain.name}
+        </option>
+      ))}
+    </select>
+  );
+}