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

Dockerfile

@@ -66,6 +66,7 @@ RUN pnpm install --frozen-lockfile
 # Copy backend build artifacts
 COPY --from=backend-builder /app/packages/backend/dist ./packages/backend/dist
 COPY --from=backend-builder /app/packages/backend/prisma ./packages/backend/prisma
+COPY --from=backend-builder /app/packages/backend/scripts ./packages/backend/scripts
 
 # Copy Prisma generated client (in pnpm workspace structure)
 # We need to copy the entire .pnpm directory to preserve the Prisma client