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/GoalSummary.svelte

@@ -2,8 +2,10 @@
   import {now, DAY, uniq, sum} from "@welshman/lib"
   import type {Zap, TrustedEvent} from "@welshman/util"
   import {getTagValue, fromMsats, ZAP_RESPONSE} from "@welshman/util"
-  import {deriveItemsByKey, deriveArray} from "@welshman/store"
-  import {repository, getValidZap} from "@welshman/app"
+  import {derived} from "svelte/store"
+  import {deriveEvents} from "@welshman/store"
+  import {app, repository} from "@app/welshman"
+  import {Zappers} from "@welshman/app"
   import Bolt from "@assets/icons/bolt.svg?dataurl"
   import Icon from "@lib/components/Icon.svelte"
   import ZapButton from "@app/components/ZapButton.svelte"
@@ -16,13 +18,15 @@
 
   const {url, event, ...props}: Props = $props()
 
-  const zaps = deriveArray(
-    deriveItemsByKey<Zap>({
-      repository,
-      getKey: zap => zap.response.id,
-      filters: [{kinds: [ZAP_RESPONSE], "#e": [event.id]}],
-      eventToItem: (response: TrustedEvent) => getValidZap(response, event),
-    }),
+  // Validated zaps for this goal. `validZapReceipts` is a reactive Projection
+  // (resolves recipient zappers from loaded profiles); we re-derive it whenever
+  // the set of ZAP_RESPONSE events in the repository changes.
+  const zapReceipts = deriveEvents({repository, filters: [{kinds: [ZAP_RESPONSE], "#e": [event.id]}]})
+  const zaps = derived(
+    zapReceipts,
+    ($receipts: TrustedEvent[], set) =>
+      app.use(Zappers).validZapReceipts($receipts, event).$.subscribe(set),
+    [] as Zap[],
   )
 
   const goalAmount = parseInt(getTagValue("amount", event.tags) || "0")