refactor: rebrand decp.info to colibre #57

- Rename project from decp.info to colibre across all codebase
- Update domain from https://decp.info to https://colibre.fr
- Update GitHub repo references to ColinMaudry/colibre
- Rename deployment files: decpinfo-backup.* → colibre-backup.*
- Update project configuration and documentation
- Rename project assets: decp.info.png → colibre.png
- Update environment variables and constants (DOMAIN_NAME, TOKEN_PREFIX, GITHUB_REPO, etc.)
- Update URLs in all pages, tests, and configuration files
- Keep DECP acronym in text (unchanged per requirements)
- Add rebrand note to README.md

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

src/pages/a-propos.py

@@ -5,9 +5,9 @@ from src.utils.seo import META_CONTENT
 register_page(
     __name__,
     path="/a-propos",
-    title="À propos | decp.info",
+    title="À propos | colibre",
     name="À propos",
-    description="En savoir plus sur decp.info, l'outil d'exploration des données essentielles de la commande publique.",
+    description="En savoir plus sur colibre, l'outil d'exploration des données essentielles de la commande publique.",
     image_url=META_CONTENT["image_url"],
     order=5,
 )