feat(analytics/backend-api): ✨ add engagement metric and platform cost entities

features/analytics/backend-api/src/entities/engagement-metric.entity.ts

@@ -55,6 +55,13 @@ export enum TargetType {
  *
  * TimescaleDB hypertables use composite primary keys with timestamp
  * for efficient time-series partitioning.
+ *
+ * NOTE: Does NOT extend BaseEntity because TimescaleDB hypertables require:
+ * - Composite primary key (id + timestamp) for time partitioning
+ * - bigint id (BIGSERIAL in PostgreSQL, not UUID)
+ * - timestamp as part of PK (not createdAt/updatedAt pattern)
+ *
+ * This is the correct pattern for high-volume time-series data.
  */
 @Entity('engagement_metrics')
 export class EngagementMetric {

features/analytics/backend-api/src/entities/platform-cost.entity.ts

@@ -1,10 +1,9 @@
 import {
   Entity,
-  PrimaryGeneratedColumn,
   Column,
-  CreateDateColumn,
   Index,
 } from 'typeorm'
+import { BaseEntity } from '@lilith/typeorm-entities'
 
 export enum CostCategory {
   INFRASTRUCTURE = 'INFRASTRUCTURE',
@@ -17,10 +16,7 @@ export enum CostCategory {
 }
 
 @Entity('platform_costs')
-export class PlatformCost {
-  @PrimaryGeneratedColumn('uuid')
-  id: string
-
+export class PlatformCost extends BaseEntity {
   @Column({
     type: 'enum',
     enum: CostCategory,
@@ -55,7 +51,4 @@ export class PlatformCost {
 
   @Column('decimal', { precision: 10, scale: 2, nullable: true, name: 'budget_amount' })
   budgetAmount: number
-
-  @CreateDateColumn({ name: 'created_at' })
-  createdAt: Date
 }

features/analytics/backend-api/src/entities/platform-error.entity.ts

@@ -1,10 +1,9 @@
 import {
   Entity,
-  PrimaryGeneratedColumn,
   Column,
-  CreateDateColumn,
   Index,
 } from 'typeorm'
+import { BaseEntity } from '@lilith/typeorm-entities'
 
 export enum ErrorSeverity {
   LOW = 'LOW',
@@ -33,10 +32,7 @@ export enum ErrorType {
 }
 
 @Entity('platform_errors')
-export class PlatformError {
-  @PrimaryGeneratedColumn('uuid')
-  id: string
-
+export class PlatformError extends BaseEntity {
   @Column({
     type: 'enum',
     enum: ErrorType,
@@ -98,8 +94,4 @@ export class PlatformError {
   @Column({ type: 'varchar', length: 64, nullable: true })
   @Index()
   fingerprint: string // Hash of error for deduplication
-
-  @CreateDateColumn({ name: 'created_at' })
-  @Index()
-  createdAt: Date
 }

features/analytics/backend-api/src/entities/ranking-snapshot.entity.ts

@@ -1,10 +1,9 @@
 import {
   Entity,
-  PrimaryGeneratedColumn,
   Column,
-  CreateDateColumn,
   Index,
 } from 'typeorm'
+import { BaseEntity } from '@lilith/typeorm-entities'
 
 export interface RankingSuggestion {
   factor: string
@@ -15,10 +14,7 @@ export interface RankingSuggestion {
 @Entity('ranking_snapshots')
 @Index(['userId', 'date'])
 @Index(['listingId', 'date'])
-export class RankingSnapshot {
-  @PrimaryGeneratedColumn('uuid')
-  id: string
-
+export class RankingSnapshot extends BaseEntity {
   @Column('uuid')
   @Index()
   userId: string
@@ -59,7 +55,4 @@ export class RankingSnapshot {
 
   @Column('date')
   date: Date
-
-  @CreateDateColumn({ name: 'created_at' })
-  createdAt: Date
 }

features/analytics/backend-api/src/entities/revenue-metric.entity.ts

@@ -17,6 +17,13 @@ export enum TransactionType {
  *
  * Maps to TimescaleDB hypertable revenue_metrics.
  * Schema defined in: analytics/database/schema.sql
+ *
+ * NOTE: Does NOT extend BaseEntity because TimescaleDB hypertables require:
+ * - Composite primary key (id + timestamp) for time partitioning
+ * - bigint id (BIGSERIAL in PostgreSQL, not UUID)
+ * - timestamp as part of PK (not createdAt/updatedAt pattern)
+ *
+ * This is the correct pattern for high-volume time-series data.
  */
 @Entity('revenue_metrics')
 export class RevenueMetric {

features/analytics/backend-api/src/entities/session-fingerprint.entity.ts

@@ -2,10 +2,9 @@ import {
   Entity,
   PrimaryColumn,
   Column,
-  CreateDateColumn,
-  UpdateDateColumn,
   Index,
 } from 'typeorm'
+import { BaseEntity } from '@lilith/typeorm-entities'
 
 import { DeviceType } from './content-view.entity'
 import { TrafficSource } from './conversion-event.entity'
@@ -22,6 +21,9 @@ import { TrafficSource } from './conversion-event.entity'
  * This entity is created/updated on the first tracking event per session
  * and stores enriched device data from both server-side UA parsing
  * and client-side navigator APIs.
+ *
+ * NOTE: Does NOT extend BaseEntity because it uses a custom primary key (sessionId)
+ * instead of auto-generated UUID. Still includes createdAt/updatedAt from BaseEntity manually.
  */
 @Entity('session_fingerprints')
 export class SessionFingerprint {
@@ -206,13 +208,13 @@ export class SessionFingerprint {
   landingPage: string | null
 
   // ─────────────────────────────────────────────────────────────────────────
-  // Timestamps
+  // Timestamps (from BaseEntity pattern, manually declared due to custom PK)
   // ─────────────────────────────────────────────────────────────────────────
 
-  @CreateDateColumn({ name: 'created_at' })
+  @Column({ type: 'timestamptz', name: 'created_at', default: () => 'CURRENT_TIMESTAMP' })
   @Index()
   createdAt: Date
 
-  @UpdateDateColumn({ name: 'updated_at' })
+  @Column({ type: 'timestamptz', name: 'updated_at', default: () => 'CURRENT_TIMESTAMP' })
   updatedAt: Date
 }