feat : initial PostgreSQL infrastructure setup

- docker-compose with postgres:16-alpine
- Init script to create databases (SIRH + Ferme, prod + recette)
- Deploy script with readiness check
- Backup script with rotation (keeps last 7)
- Auto-tag CI workflow
- Full deployment documentation

.gitea/workflows/auto-tag.yml

@@ -0,0 +1,43 @@
+name: Auto Tag
+
+on:
+  push:
+    branches:
+      - main
+
+jobs:
+  tag:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
+          token: ${{ secrets.REGISTRY_TOKEN }}
+          persist-credentials: true
+
+      - name: Create next tag
+        shell: bash
+        run: |
+          set -euo pipefail
+
+          if git tag --points-at HEAD | grep -qE '^v[0-9]+\.[0-9]+\.[0-9]+$'; then
+            echo "Tag already exists on this commit. Skipping."
+            exit 0
+          fi
+
+          last_tag="$(git tag -l 'v*' --sort=-v:refname | head -n1 || true)"
+          if [ -z "$last_tag" ]; then
+            version="0.1.0"
+          else
+            base="${last_tag#v}"
+            IFS='.' read -r major minor patch <<< "$base"
+            version="${major}.${minor}.$((patch + 1))"
+          fi
+
+          tag="v$version"
+          git config user.name "gitea-actions"
+          git config user.email "gitea-actions@local"
+          git tag "$tag"
+          git push origin "$tag"
+          echo "Tagged: $tag"