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/ThunkStatusOrDeleted.svelte

@@ -3,7 +3,8 @@
   import type {TrustedEvent} from "@welshman/util"
   import {PublishStatus} from "@welshman/net"
   import {deriveIsDeleted} from "@welshman/store"
-  import {thunks, mergeThunks, thunkHasStatus, repository} from "@welshman/app"
+  import {Thunks} from "@welshman/app"
+  import {app, thunks, repository} from "@app/welshman"
   import ThunkStatus from "@app/components/ThunkStatus.svelte"
 
   type Props = {
@@ -14,12 +15,12 @@
   const {event, children}: Props = $props()
 
   const deleted = deriveIsDeleted(repository, event)
-  const thunk = $derived(mergeThunks($thunks.filter(t => t.event.id === event.id)))
+  const thunk = $derived(app.use(Thunks).merge($thunks.filter(t => t.event.id === event.id)))
 </script>
 
 {#if $deleted}
   <div class="btn btn-error btn-xs rounded-full">Deleted</div>
-{:else if thunk.thunks.length > 0 && !thunkHasStatus(PublishStatus.Success, thunk)}
+{:else if thunk.thunks.length > 0 && !thunk.hasStatus(PublishStatus.Success)}
   <ThunkStatus {thunk} />
 {:else if children}
   {@render children?.()}