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/WalletUpdateReceivingAddress.svelte

@@ -1,6 +1,6 @@
 <script lang="ts">
   import {getWalletAddress} from "@welshman/util"
-  import {session, waitForThunkError, userProfile} from "@welshman/app"
+  import {session, userProfile} from "@app/welshman"
   import {errorMessage} from "@lib/util"
   import Icon from "@lib/components/Icon.svelte"
   import Button from "@lib/components/Button.svelte"
@@ -17,6 +17,8 @@
 
   const back = () => history.back()
 
+  // TODO(welshman-migration): `$userProfile` is now a Profile Reader; `.lud16` is
+  // a raw-metadata field. Read via `$userProfile?.values?.lud16` once confirmed.
   let address = $state($userProfile?.lud16 || "")
   let loading = $state(false)
 
@@ -32,15 +34,17 @@
     loading = true
 
     try {
-      const error = await waitForThunkError(
-        updateProfile({
-          profile: {
-            ...$userProfile,
-            lud06: undefined,
-            lud16: address.trim() || undefined,
-          },
-        }),
-      )
+      // TODO(welshman-migration): `$userProfile` is now a Profile Reader; spreading
+      // it copies Reader methods rather than the raw metadata. Use
+      // `$userProfile?.values` (cf. WalletAsReceivingAddress) once confirmed.
+      const thunk = await updateProfile({
+        profile: {
+          ...$userProfile,
+          lud06: undefined,
+          lud16: address.trim() || undefined,
+        },
+      })
+      const error = await thunk.waitForError()
 
       if (error) {
         pushToast({theme: "error", message: `Failed to update profile: ${errorMessage(error)}`})