Add .env.example with documented config

.env.example

@@ -0,0 +1,20 @@
+# Server port (default: 3012)
+PORT=3012
+
+# Base URL for the Appwrite API.
+# Override only if your Appwrite instance lives somewhere other than the default.
+APPWRITE_BASE_URL=https://appwrite.bsidesolutions.net/v1
+
+# JSON map: slot name → { project, apiKey }
+# Set this in your hosting platform's environment variables, NOT in this file.
+#
+# Example:
+# PROJECT_CREDENTIALS={"square":{"project":"staging-crown-x-ms-monet","key":"<your-appwrite-api-key>"}}
+PROJECT_CREDENTIALS=
+
+# Short-path route map. Format: "/path=>{apiKeySlot,functionId}"
+# Multiple routes separated by ';'
+#
+# Example:
+# ROUTE_MAP=/square=>{"apiKeySlot":"square","functionId":"verify_square_webhook"}
+ROUTE_MAP=