Fix regenerate-all-gifs script for production environment

Problem: Script failed in production Docker container because it tried
to import from '../src/utils/gifGenerator.js' which doesn't exist in
production (only compiled dist/ directory exists).

Error:
  Cannot find module '/app/packages/backend/src/utils/gifGenerator.js'

Solution: Use dynamic import with path detection to support both
development and production environments.

Changes:
- Check if dist/utils/gifGenerator.js exists (production)
- Fall back to src/utils/gifGenerator.js (development)
- Use dynamic import with await to load the correct module

This allows the script to work in both:
- Development: npx tsx scripts/regenerate-all-gifs.ts
- Production: Docker container with REGENERATE_GIFS=true

Tested: Docker container now starts successfully and executes the
GIF regeneration script without errors.

Co-Authored-By: Auggie

packages/backend/scripts/regenerate-all-gifs.ts

@@ -1,5 +1,4 @@
 import { PrismaClient, MediaKind } from '@prisma/client';
-import { generateGifFromVideo } from '../src/utils/gifGenerator.js';
 import path from 'path';
 import fs from 'fs';
 import { fileURLToPath } from 'url';
@@ -7,6 +6,13 @@ import { fileURLToPath } from 'url';
 const __filename = fileURLToPath(import.meta.url);
 const __dirname = path.dirname(__filename);
 
+// Dynamic import to support both dev (src/) and production (dist/)
+const gifGeneratorPath = fs.existsSync(path.join(__dirname, '../dist/utils/gifGenerator.js'))
+  ? '../dist/utils/gifGenerator.js'
+  : '../src/utils/gifGenerator.js';
+
+const { generateGifFromVideo } = await import(gifGeneratorPath);
+
 const prisma = new PrismaClient();
 
 async function regenerateAllGifs() {