Add homepage, tarifs, legal pages, navbar, footer and full test coverage

- Homepage: hero, how it works (buyer/organizer), features, CTA
- Tarifs: 3 plans (Gratuit, Basique 10€, Sur-mesure), JSON-LD Product
- Legal pages: mentions legales, CGU (tabs buyer/organizer), CGV, RGPD, cookies, hosting
- Navbar: neubrutalism style, logo liip, mobile menu, SEO attributes
- Footer: contact, description, legal links, tarifs
- Sitemap: add /tarifs and /sitemap-orgas-{page}.xml
- Liip Imagine: remove S3, webp format on all filters
- Tests: full coverage for all controllers, services, repositories
- Fix CSP: replace inline onclick with data-tab JS

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Makefile

@@ -55,6 +55,12 @@ clear_prod: ## Clear le cache Symfony et le pool opcache en prod via Docker
 	docker compose -f docker-compose-prod.yml exec php php bin/console cache:clear --env=prod
 	docker compose -f docker-compose-prod.yml exec php php bin/console cache:pool:clear --all --env=prod
 
+purge_liip_dev: ## Purge le cache Liip Imagine en dev via Docker
+	docker compose -f docker-compose-dev.yml exec php php bin/console liip:imagine:cache:remove
+
+purge_liip_prod: ## Purge le cache Liip Imagine en prod via Docker
+	docker compose -f docker-compose-prod.yml exec php php bin/console liip:imagine:cache:remove --env=prod
+
 ## —— Maintenance ——————————————————————————————————
 maintenance_on: ## Active le mode maintenance
 	touch public/.update