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>

tests/auth/test_mailer_integration.py

@@ -17,5 +17,5 @@ def test_send_verification_email_sandbox(monkeypatch):
     mailer.init_mailer()
     # Ne doit pas lever : l'API Brevo accepte la requête en sandbox.
     mailer.send_verification_email(
-        os.getenv("MAIL_FROM", "noreply@decp.info"), "INTEGRATION_TOKEN"
+        os.getenv("MAIL_FROM", "noreply@colibre"), "INTEGRATION_TOKEN"
     )