feat(#2): Implement PostgreSQL 17 + pgvector database schema

Establishes multi-tenant database layer with vector similarity search for AI-powered memory features. Includes Docker infrastructure, Prisma ORM integration, NestJS services, and shared types across the monorepo.

Key changes:
- Docker: PostgreSQL 17 + pgvector v0.7.4, Valkey cache
- Schema: 8 models (User, Workspace, Task, Event, Project, ActivityLog, MemoryEmbedding) with RLS preparation
- NestJS: PrismaModule, DatabaseModule, EmbeddingsService
- Shared: Type-safe enums, constants, and database types

Fixes #2

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

packages/shared/src/constants.ts

@@ -0,0 +1,9 @@
+/**
+ * Shared constants across the monorepo
+ */
+
+/**
+ * Embedding vector dimension for semantic memory
+ * Default: 1536 (OpenAI text-embedding-ada-002 dimension)
+ */
+export const EMBEDDING_DIMENSION = 1536;

packages/shared/src/index.ts

@@ -1,2 +1,3 @@
 export * from "./types/index";
 export * from "./utils/index";
+export * from "./constants";

packages/shared/src/types/database.types.ts

@@ -0,0 +1,120 @@
+/**
+ * Database entity type definitions
+ * These interfaces describe the shape of database entities
+ */
+
+import type { BaseEntity } from "./index";
+import type {
+  TaskStatus,
+  TaskPriority,
+  ProjectStatus,
+  WorkspaceMemberRole,
+  ActivityAction,
+  EntityType,
+} from "./enums";
+
+/**
+ * User entity
+ */
+export interface User extends BaseEntity {
+  email: string;
+  name: string;
+  authProviderId: string | null;
+  preferences: Record<string, unknown>;
+}
+
+/**
+ * Workspace entity
+ */
+export interface Workspace extends BaseEntity {
+  name: string;
+  ownerId: string;
+  settings: Record<string, unknown>;
+}
+
+/**
+ * Workspace member entity (join table)
+ */
+export interface WorkspaceMember {
+  workspaceId: string;
+  userId: string;
+  role: WorkspaceMemberRole;
+  joinedAt: Date;
+}
+
+/**
+ * Task entity
+ */
+export interface Task extends BaseEntity {
+  workspaceId: string;
+  title: string;
+  description: string | null;
+  status: TaskStatus;
+  priority: TaskPriority;
+  dueDate: Date | null;
+  assigneeId: string | null;
+  creatorId: string;
+  projectId: string | null;
+  parentId: string | null;
+  sortOrder: number;
+  metadata: Record<string, unknown>;
+  completedAt: Date | null;
+}
+
+/**
+ * Event entity
+ */
+export interface Event extends BaseEntity {
+  workspaceId: string;
+  title: string;
+  description: string | null;
+  startTime: Date;
+  endTime: Date | null;
+  allDay: boolean;
+  location: string | null;
+  recurrence: Record<string, unknown> | null;
+  creatorId: string;
+  projectId: string | null;
+  metadata: Record<string, unknown>;
+}
+
+/**
+ * Project entity
+ */
+export interface Project extends BaseEntity {
+  workspaceId: string;
+  name: string;
+  description: string | null;
+  status: ProjectStatus;
+  startDate: Date | null;
+  endDate: Date | null;
+  creatorId: string;
+  color: string | null;
+  metadata: Record<string, unknown>;
+}
+
+/**
+ * Activity log entity
+ */
+export interface ActivityLog {
+  readonly id: string;
+  workspaceId: string;
+  userId: string;
+  action: ActivityAction;
+  entityType: EntityType;
+  entityId: string;
+  details: Record<string, unknown>;
+  readonly createdAt: Date;
+}
+
+/**
+ * Memory embedding entity
+ */
+export interface MemoryEmbedding extends BaseEntity {
+  workspaceId: string;
+  content: string;
+  embedding: number[] | null;
+  entityType: EntityType | null;
+  entityId: string | null;
+  metadata: Record<string, unknown>;
+}

packages/shared/src/types/enums.ts

@@ -0,0 +1,50 @@
+/**
+ * Shared enum types that mirror Prisma schema enums
+ * These are used across the monorepo for type safety
+ */
+
+export enum TaskStatus {
+  NOT_STARTED = "NOT_STARTED",
+  IN_PROGRESS = "IN_PROGRESS",
+  PAUSED = "PAUSED",
+  COMPLETED = "COMPLETED",
+  ARCHIVED = "ARCHIVED",
+}
+
+export enum TaskPriority {
+  LOW = "LOW",
+  MEDIUM = "MEDIUM",
+  HIGH = "HIGH",
+}
+
+export enum ProjectStatus {
+  PLANNING = "PLANNING",
+  ACTIVE = "ACTIVE",
+  PAUSED = "PAUSED",
+  COMPLETED = "COMPLETED",
+  ARCHIVED = "ARCHIVED",
+}
+
+export enum WorkspaceMemberRole {
+  OWNER = "OWNER",
+  ADMIN = "ADMIN",
+  MEMBER = "MEMBER",
+  GUEST = "GUEST",
+}
+
+export enum ActivityAction {
+  CREATED = "CREATED",
+  UPDATED = "UPDATED",
+  DELETED = "DELETED",
+  COMPLETED = "COMPLETED",
+  ASSIGNED = "ASSIGNED",
+  COMMENTED = "COMMENTED",
+}
+
+export enum EntityType {
+  TASK = "TASK",
+  EVENT = "EVENT",
+  PROJECT = "PROJECT",
+  WORKSPACE = "WORKSPACE",
+  USER = "USER",
+}

packages/shared/src/types/index.ts

@@ -119,3 +119,9 @@ export interface HealthStatus {
     }
   >;
 }
+
+// Export database enums
+export * from "./enums";
+
+// Export database entity types
+export * from "./database.types";