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/api/prisma/migrations/20260129234950_add_personality_model/migration.sql

@@ -0,0 +1,31 @@
+-- CreateEnum
+CREATE TYPE "FormalityLevel" AS ENUM ('VERY_CASUAL', 'CASUAL', 'NEUTRAL', 'FORMAL', 'VERY_FORMAL');
+
+-- CreateTable
+CREATE TABLE "personalities" (
+    "id" UUID NOT NULL,
+    "workspace_id" UUID NOT NULL,
+    "name" TEXT NOT NULL,
+    "description" TEXT,
+    "tone" TEXT NOT NULL,
+    "formality_level" "FormalityLevel" NOT NULL DEFAULT 'NEUTRAL',
+    "system_prompt_template" TEXT NOT NULL,
+    "is_default" BOOLEAN NOT NULL DEFAULT false,
+    "is_active" BOOLEAN NOT NULL DEFAULT true,
+    "created_at" TIMESTAMPTZ NOT NULL DEFAULT CURRENT_TIMESTAMP,
+    "updated_at" TIMESTAMPTZ NOT NULL,
+
+    CONSTRAINT "personalities_pkey" PRIMARY KEY ("id")
+);
+
+-- CreateIndex
+CREATE INDEX "personalities_workspace_id_idx" ON "personalities"("workspace_id");
+
+-- CreateIndex
+CREATE INDEX "personalities_workspace_id_is_default_idx" ON "personalities"("workspace_id", "is_default");
+
+-- CreateIndex
+CREATE UNIQUE INDEX "personalities_workspace_id_name_key" ON "personalities"("workspace_id", "name");
+
+-- AddForeignKey
+ALTER TABLE "personalities" ADD CONSTRAINT "personalities_workspace_id_fkey" FOREIGN KEY ("workspace_id") REFERENCES "workspaces"("id") ON DELETE CASCADE ON UPDATE CASCADE;