feat(fase-12): section visibility model — feature_flags + section_enabled()

Adds JSONB `feature_flags` columns on public.users and public.collectives
(default '{}') plus two SQL helpers:

  * public.known_sections() — IMMUTABLE, returns the canonical 4 sections
    (lists, tasks, notes, search). Adding a section is a fresh migration.
  * public.section_enabled(section, user, collective) — STABLE, returns
    boolean. Precedence is COLLECTIVE > USER > default TRUE, evaluated as
    a single COALESCE so Fase 13 can prepend a server layer as a one-line
    diff. Unknown section keys default TRUE (forward-compat).

No new RLS policy: writes to feature_flags piggyback on users_update_own
and collectives_update (migration 003). 16 new pgTAP assertions verify
column shape, function signatures, volatility, and precedence semantics.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

packages/types/src/database.ts

@@ -33,6 +33,7 @@ export interface Database {
 					avatar_emoji: string | null;
 					avatar_url: string | null;
 					theme: ThemeMode;
+					feature_flags: Json;
 					created_at: string;
 					updated_at: string;
 				};
@@ -45,6 +46,7 @@ export interface Database {
 					avatar_emoji?: string | null;
 					avatar_url?: string | null;
 					theme?: ThemeMode;
+					feature_flags?: Json;
 					created_at?: string;
 					updated_at?: string;
 				};
@@ -57,6 +59,7 @@ export interface Database {
 					avatar_emoji?: string | null;
 					avatar_url?: string | null;
 					theme?: ThemeMode;
+					feature_flags?: Json;
 					created_at?: string;
 					updated_at?: string;
 				};
@@ -68,6 +71,7 @@ export interface Database {
 					name: string;
 					emoji: string;
 					created_by: string;
+					feature_flags: Json;
 					created_at: string;
 				};
 				Insert: {
@@ -75,6 +79,7 @@ export interface Database {
 					name: string;
 					emoji?: string;
 					created_by: string;
+					feature_flags?: Json;
 					created_at?: string;
 				};
 				Update: {
@@ -82,6 +87,7 @@ export interface Database {
 					name?: string;
 					emoji?: string;
 					created_by?: string;
+					feature_flags?: Json;
 					created_at?: string;
 				};
 				Relationships: [
@@ -485,6 +491,14 @@ export interface Database {
 				Args: { p_item_id: string };
 				Returns: string;
 			};
+			known_sections: {
+				Args: Record<string, never>;
+				Returns: string[];
+			};
+			section_enabled: {
+				Args: { p_section: string; p_user: string; p_collective: string };
+				Returns: boolean;
+			};
 		};
 		Enums: {
 			language_code: LanguageCode;