feat(play-standalone): Add PEER_URL env variable (#302)

## Description

Adds PEER_URL env variable for setting peer URL (query param still takes
priority if set).

- Useful for self-hosters
- Was a pain to figure out



<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->

## Summary by CodeRabbit

- New Features
- Support configuring the peer server URL via an environment variable,
with automatic fallback to the URL parameter or a default.
- Server-provided configuration is securely passed to the client to
simplify deployment setup.

- Chores
- Excluded common build artifacts and IDE directories from container
contexts to reduce image size and speed up builds.

<!-- end of auto-generated comment: release notes by coderabbit.ai -->

Co-authored-by: DatCaptainHorse <DatCaptainHorse@users.noreply.github.com>

packages/play-standalone/.containerignore

@@ -0,0 +1,4 @@
+.astro/
+.idea/
+dist/
+node_modules/

packages/play-standalone/astro.config.mjs

@@ -1,5 +1,5 @@
 // @ts-check
-import { defineConfig } from "astro/config";
+import { defineConfig, envField } from "astro/config";
 import node from "@astrojs/node";
 
 // https://astro.build/config
@@ -12,4 +12,9 @@ export default defineConfig({
     "host": "0.0.0.0",
     "port": 3000,
   },
+  env: {
+    schema: {
+      PEER_URL: envField.string({ context: "server", access: "secret", optional: true }),
+    }
+  }
 });

packages/play-standalone/src/pages/[room].astro

@@ -1,16 +1,36 @@
 ---
 import DefaultLayout from "../layouts/DefaultLayout.astro";
 const { room } = Astro.params;
+
+// Passing of environment variables to the client side
+// gotta love node and it's ecosystem..
+const envs_map: Map<string, string | undefined> = new Map();
+import { PEER_URL, getSecret } from "astro:env/server";
+if (PEER_URL) {
+	envs_map.set("PEER_URL", getSecret("PEER_URL"));
+}
+
+let envs: string = "";
+if (envs_map.size > 0) {
+	envs = JSON.stringify(Array.from(envs_map.entries()));
+}
 ---
 
 <DefaultLayout>
 	<h1 id="offlineText" class="offline">Offline</h1>
 	<h1 id="loadingText" class="loading">Warming up the GPU...</h1>
 	<canvas id="playCanvas" class="playCanvas" data-room={room}></canvas>
+	<div id="ENVS" data-envs={envs}></div>
 </DefaultLayout>
 
 <script>
 	import { Mouse, Keyboard, WebRTCStream } from "@nestri/input";
+	const ENVS = document.getElementById("ENVS")!.dataset.envs as string;
+	let ENVS_MAP: Map<string, string | undefined> | null = null;
+	if (ENVS && ENVS.length > 0) {
+		ENVS_MAP = new Map(JSON.parse(ENVS));
+		console.debug("ENVS_MAP:", ENVS_MAP);
+	}
 
 	// Elements
 	const canvas = document.getElementById("playCanvas")! as HTMLCanvasElement;
@@ -28,9 +48,11 @@ const { room } = Astro.params;
 	// Get query parameter "peerURL" from the URL
 	let peerURL = new URLSearchParams(window.location.search).get("peerURL");
 	if (!peerURL || peerURL.length <= 0) {
-		peerURL = "/dnsaddr/relay.dathorse.com/p2p/12D3KooWPK4v5wKYNYx9oXWjqLM8Xix6nm13o91j1Feqq98fLBsw";
+		peerURL = (ENVS_MAP && ENVS_MAP.get("PEER_URL")) ?? "/dnsaddr/relay.dathorse.com/p2p/12D3KooWPK4v5wKYNYx9oXWjqLM8Xix6nm13o91j1Feqq98fLBsw";
 	}
 
+	console.debug("Using Peer URL:", peerURL);
+
 	// Stream
 	const stream = new WebRTCStream(peerURL, room, async (mediaStream) => {
 		if (mediaStream && video.srcObject === null) {