chore: clear audit backlog (types sync, email norm, docs, members shortcut)

Finishes all remaining tracked work from the full-app audit.

- types/database.ts synced: added the 8 missing tables (forum_threads,
  comments, space_tiers, space_invites, space_onboarding_steps,
  space_role_labels, space_custom_roles, space_member_custom_roles),
  the comment_entity_type enum (type + Constants), and the missing
  columns (space_members.tier_id/onboarding_completed_at/
  onboarding_progress, secrets.encrypted_value/encryption_version,
  knowledge_base.render_markdown).
- Email canonicalization: new emailField() helper (trim+lowercase)
  applied to signIn/signUp/addMember/updateMember/createContact and
  the import path; prevents case-variant duplicates and sign-in
  mismatches.
- Members directory: per-row "make area lead" picker (admin/board)
  assigns a member to any area-lead role; mirrors Customize.
- Docs refreshed and re-dated: DATABASE_SCHEMA.md (migrations 014-024
  summary), DB_SCHEMA_MAP.md (new-table quick map), API_REFERENCE.md
  (all server actions from migrations 016-024). schema.sql named as
  source of truth.

Backlog is now empty. 271/271 tests pass, build clean. No migration.

app/(app)/members/page.tsx

@@ -57,10 +57,22 @@ export default async function MembersPage() {
     .eq('space_id', self.space_id)
     .order('joined_at')
 
+  // Area-lead roles, so admin/board can assign a lead straight from a member
+  // row (the same capability also lives in Customize -> Area leads).
+  const canManageLeads = self.role === 'admin' || self.role === 'board'
+  const { data: areaLeadRoles } = canManageLeads
+    ? await supabase
+        .from('area_leads')
+        .select('id, area_name, lead_id')
+        .eq('space_id', self.space_id)
+        .order('area_name')
+    : { data: [] }
+
   return (
     <MembersClient
       members={members ?? []}
       currentRole={self.role}
+      areaLeadRoles={(areaLeadRoles ?? []) as Array<{ id: string; area_name: string; lead_id: string | null }>}
     />
   )
 }