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/WalletAsReceivingAddress.svelte

@@ -1,7 +1,6 @@
 <script lang="ts">
-  import {makeProfile} from "@welshman/util"
   import {getWalletAddress} from "@welshman/util"
-  import {userProfile, waitForThunkError, session} from "@welshman/app"
+  import {userProfile, session} from "@app/welshman"
   import {errorMessage} from "@lib/util"
   import Button from "@lib/components/Button.svelte"
   import Spinner from "@lib/components/Spinner.svelte"
@@ -17,12 +16,14 @@
   const lud16 = getWalletAddress($session!.wallet!)
 
   const confirm = async () => {
-    const profile = $userProfile || makeProfile()
+    // $userProfile is now a Profile Reader; its raw metadata lives on `.values`.
+    const profile = {...($userProfile?.values ?? {}), lud16}
 
     loading = true
 
     try {
-      const error = await waitForThunkError(updateProfile({profile: {...profile, lud16}}))
+      const thunk = await updateProfile({profile})
+      const error = await thunk.waitForError()
 
       if (error) {
         pushToast({theme: "error", message: `Failed to update profile: ${errorMessage(error)}`})
@@ -46,7 +47,7 @@
     <ModalHeader>
       <ModalTitle>Set as Receiving Address?</ModalTitle>
     </ModalHeader>
-    {#if $userProfile?.lud16}
+    {#if $userProfile?.values?.lud16}
       <p>
         Your current receiving address is different from the one provided by your connected wallet.
       </p>