Anonymize sensitive information and add SSH setup documentation

Documentation:
- Add comprehensive SSH key setup guide in docs/SSH-SETUP.md
- Add SSH configuration sections to README.md and QUICKSTART.md
- Replace specific provider examples with generic alternatives
- Remove Hetzner/BorgBase specific instructions for broader applicability

Anonymization:
- Remove company/project specific names (Agence66 → generic)
- Generalize service names (/srv/app → /srv/*)
- Remove detailed application lists (/opt/nextcloud, etc. → /opt/*)
- Replace specific usernames and hostnames with placeholders
- Change repository label from 'serveur' to 'production'

Files updated:
- README.md: Add SSH setup, anonymize content
- QUICKSTART.md: Add SSH configuration steps
- CHANGELOG.md: Generalize paths list
- config.yaml: Generic title and label
- install.sh: Remove branding
- scripts/healthcheck.sh: Remove branding
- docs/SSH-SETUP.md: New comprehensive SSH guide

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

config.yaml

@@ -1,4 +1,4 @@
-# Configuration Borgmatic 2.0 pour backup serveur Agence66
+# Configuration Borgmatic 2.0 pour backup serveur
 # Compatible avec les backups Borg existants
 #
 # IMPORTANT: Nécessite Borgmatic ≥ 2.0.0 pour l'interpolation des variables d'environnement
@@ -6,7 +6,7 @@
 # Repository Borg - utilise la variable d'environnement
 repositories:
     - path: "${BORG_REPO}"
-      label: serveur
+      label: production
 
 # Chemins sources à sauvegarder
 source_directories: