Point the project at its Gitea repository

Set the manifest's links and code owner to git.asw.io/arne/ha-babytracker.
HACS can only install from GitHub, so the README now leads with a by-hand
install and describes a GitHub mirror for HACS users. Drop the HACS check
from the workflow because it cannot pass on Gitea.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

.github/workflows/validate.yml

@@ -10,12 +10,6 @@ jobs:
     steps:
       - uses: actions/checkout@v4
       - uses: home-assistant/actions/hassfest@master
-  hacs:
-    runs-on: ubuntu-latest
-    steps:
-      - uses: hacs/action@main
-        with:
-          category: integration
   tests:
     runs-on: ubuntu-latest
     steps: