Fix Docker build: include scripts directory and tsx runtime

Problem: Docker container failed to start with REGENERATE_GIFS=true
because scripts directory was not copied to production image and tsx
was not available at runtime.

Error:
  Cannot find module '/app/packages/backend/scripts/regenerate-all-gifs.ts'

Root cause:
1. Dockerfile only copied dist/ and prisma/ directories, not scripts/
2. tsx was in devDependencies, not available in production

Solution:
1. Add COPY scripts directory in Dockerfile (line 69)
2. Move tsx from devDependencies to dependencies in package.json
3. Update pnpm-lock.yaml to reflect dependency change

Changes:
- Dockerfile: Added COPY --from=backend-builder scripts directory
- package.json: Moved tsx@^4.7.0 to dependencies
- pnpm-lock.yaml: Updated lockfile

This allows the REGENERATE_GIFS environment variable to work correctly
in production, enabling automatic GIF regeneration on container startup.

Co-Authored-By: Auggie

packages/backend/package.json

@@ -32,7 +32,8 @@
     "multer": "^1.4.5-lts.1",
     "zod": "^3.22.4",
     "helmet": "^7.1.0",
-    "express-rate-limit": "^7.1.5"
+    "express-rate-limit": "^7.1.5",
+    "tsx": "^4.7.0"
   },
   "devDependencies": {
     "@types/express": "^4.17.21",
@@ -48,7 +49,6 @@
     "@typescript-eslint/parser": "^6.19.0",
     "eslint": "^8.56.0",
     "prisma": "^5.8.1",
-    "tsx": "^4.7.0",
     "typescript": "^5.3.3"
   }
 }