[web] Replace AI-Assist add-on by Overleaf AI row in the pricing pages (#31884)

* Add Overleaf AI row in the Plans pages

* Show "Overleaf AI" row only with plans-2026-phase-1

* Hide AI-Assist add-on with plans-2026-phase-1

* Update tests

GitOrigin-RevId: 905a8eede1fc460edd6da76a0988d5e8e57880fb

services/web/locales/en.json

@@ -1632,6 +1632,7 @@
   "over_n_users_at_research_institutions_and_business": "Over __userCountMillion__ million users at research institutions and businesses worldwide love __appName__",
   "overall_theme": "Overall theme",
   "overleaf": "Overleaf",
+  "overleaf_ai": "Overleaf AI",
   "overleaf_group_plans": "Overleaf group plans",
   "overleaf_history_system": "Overleaf History System",
   "overleaf_individual_plans": "Overleaf individual plans",
@@ -2597,6 +2598,7 @@
   "try_for_free": "Try for free",
   "try_it_for_free": "Try it for free",
   "try_now": "Try Now",
+  "try_overleaf_ai": "Try Overleaf AI",
   "try_premium_for_free": "Try Premium for free",
   "try_recompile_project_or_troubleshoot": "Please try recompiling the project from scratch, and if that doesn’t help, follow our <0>troubleshooting guide</0>.",
   "try_relinking_provider": "It looks like you need to re-link your __provider__ account.",
@@ -2628,6 +2630,7 @@
   "unlimited_collaborators_per_project": "Unlimited collaborators per project",
   "unlimited_collabs": "Unlimited collaborators",
   "unlimited_document_history": "Unlimited document history",
+  "unlimited_overleaf_ai": "Unlimited Overleaf AI",
   "unlimited_projects": "Unlimited projects",
   "unlink": "Unlink",
   "unlink_all_users": "Unlink all users",