test: Firebase mock harness + createCampaign characterization

- src/__mocks__/firebase/*: jest manual mocks (app/auth/firestore)
- src/__mocks__/firebase/_mock-db.js: in-memory DB + call recorder
- src/setupTests.js: jest-dom, env stubs, crypto polyfill, DB reset
- src/App.characterization.test.js: createCampaign -> setDoc path/payload locked
- src/storage/contract.js (renamed from .test.js, helper not suite)

21 tests green (memory 19 + createCampaign 2).

src/__mocks__/firebase/auth.js

@@ -0,0 +1,11 @@
+// jest manual mock: firebase/auth
+const fakeUser = { uid: 'test-user-123', isAnonymous: true };
+const fakeAuth = { currentUser: fakeUser };
+
+export function getAuth() { return fakeAuth; }
+export function signInAnonymously(auth) { return Promise.resolve({ user: fakeUser }); }
+export function signInWithCustomToken(auth, token) { return Promise.resolve({ user: fakeUser }); }
+export function onAuthStateChanged(auth, cb) {
+  cb(fakeUser);
+  return () => {};
+}