feat(fase-10): CU-H06 leave collective — RPC + settings UI

Migration 017 adds public.leave_collective(uuid) with three branches:
- normal member: remove membership row
- sole admin with other members: promote oldest-joined remaining member
  to admin (inline; the existing user-delete trigger does not cover the
  membership-delete path), then remove the row
- sole member: reject with errcode P0001 so the UI can direct the user
  to the dissolve flow (CU-H08)

Settings page gains a "Your collectives" section listing the user's
memberships with a per-row Leave button; the confirmation modal calls
the RPC, drops the collective from local stores, and either switches
to the next collective or sends the user to /onboarding when none
remain. Also seeds the Danger zone scaffolding for Fase 10.5 and adds
all message keys consumed by 10.1, 10.3, 10.5 and 10.6.

pgTAP 010 (7 assertions): member-leave, sole-admin-leave + auto-promote,
sole-member rejected with P0001. Playwright L-01 walks Borja through
the UI flow + checks the seed collective survives (content stays).

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

supabase/tests/010_leave_collective.sql

@@ -0,0 +1,111 @@
+-- pgTAP: leave_collective() RPC — Fase 10.1
+-- Run with: psql -U postgres -d postgres -f supabase/tests/010_leave_collective.sql
+--
+-- Covers CU-H06:
+--   * normal member abandons OK (membership row gone)
+--   * sole admin with other members abandons OK + oldest member auto-promoted
+--   * sole member rejected with errcode P0001 (must use dissolve_collective)
+
+CREATE EXTENSION IF NOT EXISTS pgtap;
+
+BEGIN;
+SELECT plan(7);
+
+-- ── Existence ────────────────────────────────────────────────────────────────
+SELECT has_function(
+    'public', 'leave_collective', ARRAY['uuid'],
+    'public.leave_collective(uuid) RPC exists'
+);
+
+-- ── Setup: three test users + two collectives outside seed range ──────────────
+INSERT INTO public.users (id, email, display_name, language, avatar_type)
+VALUES
+    ('e1000000-0000-0000-0000-000000000001', 'leave-admin@local',  'Leave Admin',  'es', 'initials'),
+    ('e1000000-0000-0000-0000-000000000002', 'leave-member@local', 'Leave Member', 'es', 'initials'),
+    ('e1000000-0000-0000-0000-000000000003', 'leave-solo@local',   'Leave Solo',   'es', 'initials')
+ON CONFLICT (id) DO NOTHING;
+
+-- Collective A: admin + member. created_by = Borja (so deleting admin row is safe).
+INSERT INTO public.collectives (id, name, emoji, created_by)
+VALUES ('cccccccc-1111-1111-1111-111111111111', 'Leave test A', '🚪',
+        '22222222-2222-2222-2222-222222222222')
+ON CONFLICT (id) DO NOTHING;
+
+INSERT INTO public.collective_members (collective_id, user_id, role, joined_at)
+VALUES
+    ('cccccccc-1111-1111-1111-111111111111', 'e1000000-0000-0000-0000-000000000001', 'admin',  now() - INTERVAL '10 days'),
+    ('cccccccc-1111-1111-1111-111111111111', 'e1000000-0000-0000-0000-000000000002', 'member', now() - INTERVAL '5 days')
+ON CONFLICT (collective_id, user_id) DO NOTHING;
+
+-- Collective B: sole member only.
+INSERT INTO public.collectives (id, name, emoji, created_by)
+VALUES ('cccccccc-2222-2222-2222-222222222222', 'Leave test B (solo)', '🚪',
+        '22222222-2222-2222-2222-222222222222')
+ON CONFLICT (id) DO NOTHING;
+
+INSERT INTO public.collective_members (collective_id, user_id, role)
+VALUES
+    ('cccccccc-2222-2222-2222-222222222222', 'e1000000-0000-0000-0000-000000000003', 'admin')
+ON CONFLICT (collective_id, user_id) DO NOTHING;
+
+-- ── Case 1: normal member leaves ──────────────────────────────────────────────
+-- Authenticate as leave-member
+SELECT set_config('request.jwt.claim.sub', 'e1000000-0000-0000-0000-000000000002', true);
+
+SELECT lives_ok(
+    $$ SELECT public.leave_collective('cccccccc-1111-1111-1111-111111111111') $$,
+    'L-01a: member can leave without error'
+);
+
+SELECT is(
+    (SELECT count(*)::int FROM public.collective_members
+     WHERE collective_id = 'cccccccc-1111-1111-1111-111111111111'
+     AND   user_id       = 'e1000000-0000-0000-0000-000000000002'),
+    0,
+    'L-01a: membership row removed after leave'
+);
+
+-- ── Case 2: sole admin with other members ─────────────────────────────────────
+-- Re-add the member to set up sole-admin scenario again.
+INSERT INTO public.collective_members (collective_id, user_id, role, joined_at)
+VALUES ('cccccccc-1111-1111-1111-111111111111',
+        'e1000000-0000-0000-0000-000000000002', 'member', now() - INTERVAL '5 days')
+ON CONFLICT (collective_id, user_id) DO UPDATE SET role = EXCLUDED.role;
+
+-- Authenticate as the admin
+SELECT set_config('request.jwt.claim.sub', 'e1000000-0000-0000-0000-000000000001', true);
+
+SELECT lives_ok(
+    $$ SELECT public.leave_collective('cccccccc-1111-1111-1111-111111111111') $$,
+    'L-01b: sole admin can leave when other members exist'
+);
+
+SELECT is(
+    (SELECT role::text FROM public.collective_members
+     WHERE collective_id = 'cccccccc-1111-1111-1111-111111111111'
+     AND   user_id       = 'e1000000-0000-0000-0000-000000000002'),
+    'admin',
+    'L-01b: remaining member auto-promoted to admin'
+);
+
+SELECT is(
+    (SELECT count(*)::int FROM public.collective_members
+     WHERE collective_id = 'cccccccc-1111-1111-1111-111111111111'
+     AND   user_id       = 'e1000000-0000-0000-0000-000000000001'),
+    0,
+    'L-01b: departing admin row removed'
+);
+
+-- ── Case 3: sole member tries to leave ────────────────────────────────────────
+-- Authenticate as leave-solo
+SELECT set_config('request.jwt.claim.sub', 'e1000000-0000-0000-0000-000000000003', true);
+
+SELECT throws_ok(
+    $$ SELECT public.leave_collective('cccccccc-2222-2222-2222-222222222222') $$,
+    'P0001',
+    NULL,
+    'L-01c: sole member rejected with errcode P0001'
+);
+
+SELECT * FROM finish();
+ROLLBACK;