fix: repair lib/soroban.ts + app/create mangled by the #379 merge

[mhikel66]

The #379 merge left main non-compiling. Two independent syntax/scope errors,
one hidden behind the other:

lib/soroban.ts — mangled invokeContract

invokeContract's body had a stray fragment of an inlined poll loop
(referencing an out-of-scope status, plus a leftover }, { context, signal })
from the withRetry call) wedged between the submit step and the real
return pollForConfirmation(...). tsc bailed with "Declaration or statement
expected".

• Dropped the mangled fragment.
• Finished the #362 refactor pollForConfirmation was mid-way through: it now
  returns InvokeContractResult ({ hash, returnValue }) instead of a bare
  string, capturing status.returnValue on SUCCESS so createStream can read
  the assigned stream_id.
• Exported resetFeeStatsCache() and call it in soroban-pipeline.test's
  beforeEach — the module-level fee cache leaked between test cases.

app/create/page.tsx — stale import + hand-rolled resolver (#394)

Imported isValidStellarPublicKey but the Zod schema's .refine() calls
isValidStellarAddress (never in scope).

• Import isValidStellarAddress.
• Replace the hand-rolled zodResolver (first-error-only; loose typing that
  surfaced as a FieldError-not-ReactNode error) with
  @hookform/resolvers/zod, already a dependency.

Verification (local)

npm run typecheck   # clean
npm run lint        # clean
npx vitest run      # 410 passed, 4 todo
npm run build       # 11/11 routes

Test updates: soroban-pipeline.test.ts, stream.test.ts, tokens.test.ts,
create/__tests__/page.test.tsx.

CI note

CI here stays red until two separate blockers land:

• Bug: npm ci fails on main — package-lock.json has a renamed git dep and npmmirror.com URLs, so all CI is red #404 — npm ci fails on the npmmirror.com lockfile URLs + the pre-rename
  git+ssh SDK dep (fork PRs fix(ci): point SDK to streamFi-sdk HTTPS and regenerate lockfile (Closes #404) #405 / fix: resolve assigned stream and CI issues #406 target this).
• fix(streams): repair Signer build regression from the #498 merge streamFi-sdk#555 — SDK main doesn't build (a Signer
  regression from its #498 merge), so the SDK's prepare step fails during
  npm ci even once the lockfile is fixed.

This PR is the code-repair piece and is verified locally against those.

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#341	Transactions page shows fabricated demo history to real users in production	Link to this issue
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[Jaydbrown]

This branch predates #362/#363 and the shared lib/with-timeout.ts extraction, and merging it as-is would regress main: it reverts the checkRecipientExists/settleRecipientCheck test scaffolding in app/create/__tests__/page.test.tsx (added by #363) and reintroduces the local withTimeout copy in app/create/page.tsx. The '#379 merge repair' it targets has since been resolved on main by other PRs. Closing candidate / needs a fresh rebase — leaving open per instruction.