Add one-click deploy buttons for Render and Railway

Update render.yaml to use Docker runtime with IMAP env vars so the
deploy button prompts users for credentials. Add Railway deploy link.

render.yaml

@@ -1,19 +1,19 @@
 services:
   - type: web
     name: poke-mail
-    runtime: python
-    buildCommand: pip install -r requirements.txt
-    startCommand: python src/server.py
+    runtime: docker
     plan: free
     autoDeploy: false
     envVars:
-      - key: ENVIRONMENT
-        value: production
-      - key: CONFIG_PATH
-        value: config.yml
       - key: MCP_API_KEY
-        sync: false
+        generateValue: true
       - key: POKE_WEBHOOK_URL
         sync: false
       - key: POKE_API_KEY
         sync: false
+      - key: IMAP_HOST
+        sync: false
+      - key: IMAP_USERNAME
+        sync: false
+      - key: IMAP_PASSWORD
+        sync: false