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>

pyproject.toml

@@ -1,5 +1,5 @@
 [project]
-name = "decp.info"
+name = "colibre"
 description = "Interface d'exploration et d'analyse des marchés publics français."
 version = "2.8.1"
 requires-python = ">= 3.10"
@@ -57,7 +57,7 @@ env = [
   "DATA_SCHEMA_PATH=/home/colin/git/decp-processing/dist/schema.json",
   "USERS_DB_PATH=tests/users.test.sqlite",
   "SECRET_KEY=test-secret-do-not-use-in-prod",
-  "MAIL_FROM=test@decp.info",
+  "MAIL_FROM=test@colibre.fr",
   "MAIL_SUPPRESS_SEND=true",
   "APP_BASE_URL=http://localhost:8050",
   "SMTP_HOST=localhost",