feat(#130): add Personality Prisma schema and backend

Implement Personality system backend with database schema, service,
controller, and comprehensive tests. Personalities define assistant
behavior with system prompts and LLM configuration.

Changes:
- Update Personality model in schema.prisma with LLM provider relation
- Create PersonalitiesService with CRUD and default management
- Create PersonalitiesController with REST endpoints
- Add DTOs with validation (create/update)
- Add entity for type safety
- Remove unused PromptFormatterService
- Achieve 26 tests with full coverage

Endpoints:
- GET /personality - List all
- GET /personality/default - Get default
- GET /personality/by-name/:name - Get by name
- GET /personality/:id - Get one
- POST /personality - Create
- PATCH /personality/:id - Update
- DELETE /personality/:id - Delete
- POST /personality/:id/set-default - Set default

Fixes #130

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

apps/api/src/personalities/dto/create-personality.dto.ts

@@ -1,37 +1,53 @@
-import { IsString, IsIn, IsOptional, IsBoolean, MinLength, MaxLength } from "class-validator";
-
-export const FORMALITY_LEVELS = [
-  "VERY_CASUAL",
-  "CASUAL",
-  "NEUTRAL",
-  "FORMAL",
-  "VERY_FORMAL",
-] as const;
-
-export type FormalityLevel = (typeof FORMALITY_LEVELS)[number];
+import {
+  IsString,
+  IsOptional,
+  IsBoolean,
+  IsNumber,
+  IsInt,
+  IsUUID,
+  MinLength,
+  MaxLength,
+  Min,
+  Max,
+} from "class-validator";
 
+/**
+ * DTO for creating a new personality/assistant configuration
+ */
 export class CreatePersonalityDto {
   @IsString()
   @MinLength(1)
   @MaxLength(100)
-  name!: string;
-
-  @IsOptional()
-  @IsString()
-  @MaxLength(500)
-  description?: string;
+  name!: string; // unique identifier slug
 
   @IsString()
   @MinLength(1)
-  @MaxLength(50)
-  tone!: string;
+  @MaxLength(200)
+  displayName!: string; // human-readable name
 
-  @IsIn(FORMALITY_LEVELS)
-  formalityLevel!: FormalityLevel;
+  @IsOptional()
+  @IsString()
+  @MaxLength(1000)
+  description?: string;
 
   @IsString()
   @MinLength(10)
-  systemPromptTemplate!: string;
+  systemPrompt!: string;
+
+  @IsOptional()
+  @IsNumber()
+  @Min(0)
+  @Max(2)
+  temperature?: number; // null = use provider default
+
+  @IsOptional()
+  @IsInt()
+  @Min(1)
+  maxTokens?: number; // null = use provider default
+
+  @IsOptional()
+  @IsUUID("4")
+  llmProviderInstanceId?: string; // FK to LlmProviderInstance
 
   @IsOptional()
   @IsBoolean()
@@ -39,5 +55,5 @@ export class CreatePersonalityDto {
 
   @IsOptional()
   @IsBoolean()
-  isActive?: boolean;
+  isEnabled?: boolean;
 }

apps/api/src/personalities/dto/update-personality.dto.ts

@@ -1,32 +1,56 @@
-import { IsString, IsOptional, IsBoolean, MinLength, MaxLength, IsIn } from "class-validator";
-import { FORMALITY_LEVELS, FormalityLevel } from "./create-personality.dto";
+import {
+  IsString,
+  IsOptional,
+  IsBoolean,
+  IsNumber,
+  IsInt,
+  IsUUID,
+  MinLength,
+  MaxLength,
+  Min,
+  Max,
+} from "class-validator";
 
+/**
+ * DTO for updating an existing personality/assistant configuration
+ */
 export class UpdatePersonalityDto {
   @IsOptional()
   @IsString()
   @MinLength(1)
   @MaxLength(100)
-  name?: string;
-
-  @IsOptional()
-  @IsString()
-  @MaxLength(500)
-  description?: string;
+  name?: string; // unique identifier slug
 
   @IsOptional()
   @IsString()
   @MinLength(1)
-  @MaxLength(50)
-  tone?: string;
+  @MaxLength(200)
+  displayName?: string; // human-readable name
 
   @IsOptional()
-  @IsIn(FORMALITY_LEVELS)
-  formalityLevel?: FormalityLevel;
+  @IsString()
+  @MaxLength(1000)
+  description?: string;
 
   @IsOptional()
   @IsString()
   @MinLength(10)
-  systemPromptTemplate?: string;
+  systemPrompt?: string;
+
+  @IsOptional()
+  @IsNumber()
+  @Min(0)
+  @Max(2)
+  temperature?: number; // null = use provider default
+
+  @IsOptional()
+  @IsInt()
+  @Min(1)
+  maxTokens?: number; // null = use provider default
+
+  @IsOptional()
+  @IsUUID("4")
+  llmProviderInstanceId?: string; // FK to LlmProviderInstance
 
   @IsOptional()
   @IsBoolean()
@@ -34,5 +58,5 @@ export class UpdatePersonalityDto {
 
   @IsOptional()
   @IsBoolean()
-  isActive?: boolean;
+  isEnabled?: boolean;
 }