fix: use npm instead of install script for ARM64/aarch64 support

The opencode install script (curl | sh) does not support linux/aarch64.
Switched to npm install -g opencode-ai@latest which is cross-platform.
Removed old dokploy/Dockerfile (moved to repo root).

Author: Dokploy Dev

Dockerfile

@@ -2,10 +2,7 @@ FROM codercom/code-server:latest
 
 USER root
 
-# Install opencode CLI globally
-RUN curl -fsSL https://opencode.ai/install | sh
-
-# Ensure opencode is in PATH for the coder user
-ENV PATH="${PATH}:/home/coder/.opencode/bin"
+# Install opencode CLI globally via npm (supports all architectures)
+RUN npm install -g opencode-ai@latest
 
 USER coder