Migrate to new @welshman/domain + instance-based @welshman/app API

Adopts the rewritten welshman API: the removed @welshman/util helpers
(Profile/List/Room/Handler/Encryptable) are now Reader/Builder classes in
@welshman/domain, and @welshman/app dropped its global singletons for an App
instance + app.use(Plugin) registry.

- src/app/welshman.ts is now the app bootstrap + session-state module (one shared
  App instance, multi-account sessions/login, app-wide reactive views) rather than
  a compat shim re-exporting the old globals.
- Rewrote ~100 callers to use app.use(Plugin) directly (thunks, profiles, relays,
  rooms, zaps, tags, wot, feeds, sync); thunk helpers are now thunk methods.
- Added @welshman/domain dependency.
- Resolved residual gaps (storage hydration via plugin.onItem/wrapManager/Plaintext,
  relay-list mutators, search-relay list, outbox #d filter).

Best-effort: no toolchain/linking available, so this is not build- or
type-checked. Remaining judgment calls are flagged with TODO(welshman-migration).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01BsMjvv7krpZeHK1Njeneru

src/app/components/RoomJoinItem.svelte

@@ -1,7 +1,8 @@
 <script lang="ts">
   import {getTagValue, ManagementMethod} from "@welshman/util"
-  import type {TrustedEvent, PublishedRoomMeta} from "@welshman/util"
-  import {repository, manageRelay} from "@welshman/app"
+  import type {TrustedEvent} from "@welshman/util"
+  import {RelayManagement} from "@welshman/app"
+  import {app, repository} from "@app/welshman"
   import Button from "@lib/components/Button.svelte"
   import ProfileName from "@app/components/ProfileName.svelte"
   import ProfileDetail from "@app/components/ProfileDetail.svelte"
@@ -28,7 +29,7 @@
     loading = true
 
     try {
-      const {error} = await manageRelay(url, {
+      const {error} = await app.use(RelayManagement).post(url, {
         method: ManagementMethod.BanEvent,
         params: [event.id, "Join request dismissed"],
       })
@@ -49,7 +50,11 @@
     loading = true
 
     try {
-      const error = await addRoomMembers(url, $room as PublishedRoomMeta, [event.pubkey])
+      // TODO(welshman-migration): addRoomMembers now expects a RoomMeta domain
+      // Reader, but deriveRoom yields the plain `Room` object. Passing it through
+      // as `any` preserves prior runtime behavior; verify Rooms.addMember accepts
+      // the plain Room shape (url/h/...) or resolve a real RoomMeta reader here.
+      const error = await addRoomMembers(url, $room as any, [event.pubkey])
 
       if (error) {
         pushToast({theme: "error", message: error})