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/lib/api/personalities.ts

@@ -0,0 +1,81 @@
+/**
+ * Personality API Client
+ * Handles personality-related API requests
+ */
+
+import type { Personality, FormalityLevel } from "@mosaic/shared";
+import { apiGet, apiPost, apiPatch, apiDelete, type ApiResponse } from "./client";
+
+/**
+ * Create personality DTO
+ */
+export interface CreatePersonalityDto {
+  name: string;
+  description?: string;
+  tone: string;
+  formalityLevel: FormalityLevel;
+  systemPromptTemplate: string;
+  isDefault?: boolean;
+  isActive?: boolean;
+}
+
+/**
+ * Update personality DTO
+ */
+export interface UpdatePersonalityDto {
+  name?: string;
+  description?: string;
+  tone?: string;
+  formalityLevel?: FormalityLevel;
+  systemPromptTemplate?: string;
+  isDefault?: boolean;
+  isActive?: boolean;
+}
+
+/**
+ * Fetch all personalities
+ */
+export async function fetchPersonalities(
+  isActive: boolean = true
+): Promise<ApiResponse<Personality[]>> {
+  const endpoint = `/api/personalities?isActive=${isActive}`;
+  return apiGet<ApiResponse<Personality[]>>(endpoint);
+}
+
+/**
+ * Fetch the default personality
+ */
+export async function fetchDefaultPersonality(): Promise<Personality> {
+  return apiGet<Personality>("/api/personalities/default");
+}
+
+/**
+ * Fetch a single personality by ID
+ */
+export async function fetchPersonality(id: string): Promise<Personality> {
+  return apiGet<Personality>(`/api/personalities/${id}`);
+}
+
+/**
+ * Create a new personality
+ */
+export async function createPersonality(data: CreatePersonalityDto): Promise<Personality> {
+  return apiPost<Personality>("/api/personalities", data);
+}
+
+/**
+ * Update a personality
+ */
+export async function updatePersonality(
+  id: string,
+  data: UpdatePersonalityDto
+): Promise<Personality> {
+  return apiPatch<Personality>(`/api/personalities/${id}`, data);
+}
+
+/**
+ * Delete a personality
+ */
+export async function deletePersonality(id: string): Promise<void> {
+  return apiDelete<void>(`/api/personalities/${id}`);
+}