refactor(classes): split oversize modules + bootstrap hygiene

- Trait-split content-pay, vip-service, balance-service, order-repository
- Procedural split of user module into user-parts/*
- Split scripts enqueue_public into part-1b/1c; settings bulk trait
- Bootstrap: explicit notifications, widgets glob-only, home-modules init
- ADR: freeze domain placement for pay/revenue/notify boundaries

tools/adr-classes-domain-placement.md

@@ -0,0 +1,37 @@
+# ADR: Domain folder placement for `inc/classes`
+
+## Status
+Accepted (2026-07-17)
+
+## Context
+After moving root class files into domain folders, freeze placement for boundary types so later moves are intentional.
+
+## Decision
+
+| Concern | Domain | Why |
+|---------|--------|-----|
+| Theme shell (setup, scripts, templates, SEO, meta boxes, DB migrator, front-submit, docs presenter, home modules, stats, redirects, update checker, comment actions) | `core/` | Shared CMS plumbing |
+| SPA shell + controllers + schema + native ops | `admin/` | Dual-surface IA |
+| Settings facade + runtime delegates | `settings/` | Single public settings API |
+| Auth, OAuth, captcha, moderation, email rollback | `auth/` | Identity & access |
+| User center/home/badges/level/metrics/notifications/follow | `user/` | Account surface |
+| Credits, balance wallet, signin, invite, points-free | `credits/` | Points + cash wallet |
+| Download tokens/state, content pay, VIP, visibility | `content/` | Post-centric paid content |
+| Topic pay, plate follow pay | `forum/` | Forum SKUs (not generic content pay) |
+| Orders, gateways, coupon, charge-card, revenue, creator-revenue, withdrawal, rebate, discount, after-sale, shipping, wechat-notify | `payment/` | Commerce + settlement |
+| Shop services/meta/reviews | `shop/` | Product catalog / cart |
+| SMS stack | `sms/` | Messaging channel |
+| AI runtime (admin AI controller stays in `admin/`) | `ai/` | Generation helpers |
+| Message, private message, site notice, report center | `messages/` | In-site messaging |
+| MeiliSearch, search-push, ip-geo, content-audit, api-audit | `extensions/` | Optional integrations |
+| Widgets + registry | `widgets/` | WP widgets |
+| Inline style / custom code / loading overlay | `frontend/` | Asset render helpers |
+
+### Rules
+- Traits live next to owner: `{domain}/{slug}-traits/`.
+- Loader: manual `require_once` in `inc/bootstrap.php` only; traits before shells.
+- Do not move `topic-pay` / `plate-follow-pay` into `content/` without updating this ADR.
+- `creator-revenue` and `wechat-notify` stay under `payment/`.
+
+## Out of scope
+PSR-4 class namespaces; class renames.