fix: Docker build and runtime fixes

- Fix duplicate 'signature' variable in webhooks.ts
- Add Prisma binary target for Alpine Linux
- Fix tsconfig path alias (@/* -> ./src/*)
- Add missing next-themes dependency
- Add build args for NEXT_PUBLIC_* env vars
- Fix SSR issues with zustand and providers
- Add providers-wrapper with dynamic ssr:false import
- Add SSL certs and public dir for nginx
- Update Dockerfiles for proper Prisma engine handling

backend/prisma/schema.prisma

@@ -1,5 +1,6 @@
 generator client {
-  provider = "prisma-client-js"
+  provider      = "prisma-client-js"
+  binaryTargets = ["linux-musl-openssl-3.0.x"]
 }
 
 datasource db {