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

packages/policies/src/index.ts

@@ -0,0 +1,32 @@
+// Export core types and interfaces
+export type { PolicyContext, PolicyResult, PolicyStage } from './types';
+
+// Export primary registry-based API
+export { definePolicy } from './declarative';
+export type {
+  FeaturePolicyDefinition,
+  PolicyEvaluator,
+  PolicyErrorCode,
+  PolicyReason,
+} from './declarative';
+
+// Export policy registry (primary API)
+export { createPolicyRegistry } from './registry';
+export type { PolicyRegistry } from './registry';
+
+// Export evaluator and bridge functions
+export {
+  createPolicy,
+  createPoliciesEvaluator,
+  createPolicyFromRegistry,
+  createPoliciesFromRegistry,
+} from './evaluator';
+
+export type {
+  PolicyFunction,
+  PolicyGroup,
+  EvaluationResult,
+} from './evaluator';
+
+// Export helper functions (for policy implementations)
+export { allow, deny } from './evaluator';