Feature Policies API + Invitations Policies (#375)

- Added Feature Policy API: a declarative system to enable/disable/modify default behavior in the SaaS kit
- Team invitation policies with pre-checks using the Feature Policy API: Invite Members dialog now shows loading, errors, and clear reasons when invitations are blocked
- Version bump to 2.16.0 and widespread dependency updates (Supabase, React types, react-i18next, etc.).
- Added comprehensive docs for the new policy system and orchestrators.
- Subscription cancellations now trigger immediate invoicing explicitly

apps/web/public/locales/en/teams.json

@@ -159,5 +159,17 @@
   "leaveTeamInputLabel": "Please type LEAVE to confirm leaving the team.",
   "leaveTeamInputDescription": "By leaving the team, you will no longer have access to it.",
   "reservedNameError": "This name is reserved. Please choose a different one.",
-  "specialCharactersError": "This name cannot contain special characters. Please choose a different one."
+  "specialCharactersError": "This name cannot contain special characters. Please choose a different one.",
+  "checkingPolicies": "Loading. Please wait...",
+  "policyCheckError": "We are unable to verify invitations restrictions. Please try again.",
+  "invitationsBlockedMultiple": "Invitations are currently not allowed for the following reasons:",
+  "invitationsBlockedDefault": "Invitations are currently not allowed due to policy restrictions.",
+  "policyErrors": {
+    "subscriptionRequired": "An active subscription is required to invite team members.",
+    "paddleTrialRestriction": "Cannot invite members during trial period with per-seat billing on Paddle."
+  },
+  "policyRemediation": {
+    "subscriptionRequired": "Please upgrade your plan or activate your subscription",
+    "paddleTrialRestriction": "Wait until trial period ends or upgrade to full plan"
+  }
 }