feat(beacon): ✨ Implement BeaconController with HTTP endpoints and BeaconModule providers for beacon data processing

Co-Authored-By: Lilith Autocommit <noreply@atlilith.com>

services/collector/src/beacon/beacon.controller.ts

@@ -0,0 +1,44 @@
+import { readFileSync } from 'node:fs';
+import { fileURLToPath } from 'node:url';
+import { Controller, Get, Header, Logger, NotFoundException, SetMetadata } from '@nestjs/common';
+import { IS_PUBLIC_KEY } from '../auth/write-key.guard';
+
+/**
+ * Serves the static beacon.js script at `/beacon.js` (carved out of the
+ * `/analytics` global prefix in main.ts, and marked public to bypass
+ * the WriteKeyGuard). Loaded cross-origin via
+ * `<script defer src="https://data.transquinnftw.com/beacon.js" data-site="...">`
+ * from ATT, Sansonnet, Cocotte, and SEO bait surfaces. Source of truth for
+ * the script lives in this service at public/beacon.js.
+ */
+@Controller()
+@SetMetadata(IS_PUBLIC_KEY, true)
+export class BeaconController {
+  private readonly logger = new Logger(BeaconController.name);
+  private readonly cached: string;
+
+  constructor() {
+    // ESM-safe path resolution. From dist/beacon/beacon.controller.js,
+    // ../../public/beacon.js resolves to /app/public/beacon.js in the container.
+    const path = fileURLToPath(new URL('../../public/beacon.js', import.meta.url));
+    try {
+      this.cached = readFileSync(path, 'utf8');
+      this.logger.log(`Loaded beacon.js (${this.cached.length} bytes) from ${path}`);
+    } catch (cause) {
+      const message = cause instanceof Error ? cause.message : String(cause);
+      throw new Error(`BeaconController: failed to load ${path}: ${message}`);
+    }
+  }
+
+  @Get('beacon.js')
+  @Header('Content-Type', 'application/javascript; charset=utf-8')
+  @Header('Cache-Control', 'public, max-age=300, stale-while-revalidate=600')
+  @Header('Access-Control-Allow-Origin', '*')
+  @Header('Cross-Origin-Resource-Policy', 'cross-origin')
+  serve(): string {
+    if (this.cached === undefined || this.cached.length === 0) {
+      throw new NotFoundException('beacon.js not loaded');
+    }
+    return this.cached;
+  }
+}

services/collector/src/beacon/beacon.module.ts

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+import { Module } from '@nestjs/common';
+import { BeaconController } from './beacon.controller';
+
+@Module({
+  controllers: [BeaconController],
+})
+export class BeaconModule {}