Address @qa review on PR #12 (issue #11)

- index.html: replace Image() probe with fetch(no-cors) + AbortController
  timeout. fetch resolves for any network response (incl. 4xx/5xx) so
  resolve -> 'up', reject/timeout -> 'down'. Fixes the bug where 401/404
  services were marked green.
- services.json: add Homepage service under 'dev' (was missing; the
  homepage is one of the public homelab services). Now 21 services.
- services.json: fix ethereum category icon (' Ξ' -> 'Ξ') leading space.
- .gitignore (new): ignore /.playwright-mcp/ and services-page.png.
- git rm --cached the three stray dev artifacts so they leave the repo.

services.json

@@ -39,7 +39,7 @@
     {
       "name": "ethereum",
       "label": "Ethereum",
-      "icon": " Ξ",
+      "icon": "Ξ",
       "services": [
         { "name": "Mainnet Geth", "url": "https://mainnet.ffaerber.duckdns.org", "desc": "Ethereum mainnet execution client (RPC).", "icon": "⛓️" },
         { "name": "Mainnet Beacon", "url": "https://beacon.ffaerber.duckdns.org", "desc": "Lighthouse consensus / beacon node.", "icon": "🗼" },
@@ -66,6 +66,7 @@
       "label": "Dev platform",
       "icon": "🛠️",
       "services": [
+        { "name": "Homepage", "url": "https://homepage.ffaerber.duckdns.org", "desc": "This page — the homelab services index you are looking at.", "icon": "🏠" },
         { "name": "Gitea", "url": "https://git.ffaerber.duckdns.org", "desc": "Self-hosted Git and CI for all ffaerber repos.", "icon": "🔧" }
       ]
     }