chore(js-ts): Convert transaction reducer and action module to TypeScript

[devin-ai-integration]

Summary

Workstream 4: types the transaction reducer + its action module and removes transaction: any from RootState.

The reducer state is modeled to match the transactionState shape already declared in app/core/GasPolling/types.ts (the de-facto consumer contract). Key modeling decision: the nested transaction object mixes representations — getTxData() produces BN amounts while callers like setTransactionValue(maxTransactionValueHex) and dappTransactions pass hex string/BN — so amount fields are typed string | BN:

export interface TransactionObject {
  data?: string; from?: string; to?: string;
  gas?: string | BN; gasPrice?: string | BN; value?: string | BN;
  maxFeePerGas?: string | BN; maxPriorityFeePerGas?: string | BN;
}
export interface TransactionState {
  selectedAsset: SelectedAsset;            // Record<string, unknown>
  transaction: TransactionObject;
  securityAlertResponses: Record<string, SecurityAlertResponse>;
  useMax: boolean; /* ...optional metadata fields... */
}

SecurityAlertResponse is imported from BlockaidBanner.types (not @metamask/transaction-controller) because that is the type the consumers (TransactionBlockaidBanner, ppom-util, confirmTransaction selector) actually use.

Action module now exports a discriminated-union TransactionAction (incl. a RehydrateAction so the REHYDRATE case type-checks) with typed creators.

Cascade fixes (consumers previously hidden behind any)

• selectors/confirmTransaction.ts: guard id === undefined before indexing securityAlertResponses.
• lib/ppom/ppom-util.ts: transactionId as string (matches existing cast in the same file).
• AssetOverview.tsx / WalletActions.tsx: cast asset args to SelectedAsset (getEther() is JSDoc-typed object; TokenI needs as unknown as).
• Test fixtures (AccountInfoCard, BrowserTab, Confirm, TransactionBlockaidBanner): align transaction mocks with the typed shape (selectedAsset: {}) or cast legacy-shaped fixtures.

Validation

• yarn tsc — 0 errors
• yarn lint (changed files) — 0 errors
• yarn jest on reducer + all cascade-affected suites — 13 suites / 102 tests pass

Pre-existing fork CI failures (yarn install 404 on the dead aprock/react-native-tcp git dep, CLABot, label bots) are unrelated to this change.

Link to Devin session: https://app.devin.ai/sessions/150060d9c6a14a1b9ee04e5a407b3f8b
Requested by: @WesternConcrete

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