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/_mock-db.js

@@ -0,0 +1,69 @@
+// Mock in-memory Firestore for jest tests.
+// Reset via resetMockDb() in setupTests.js beforeEach.
+
+const state = {
+  docs: new Map(),        // path -> data
+  subscribers: new Map(), // path -> Set<cb>
+  counter: 0,
+  calls: [],              // recorded SDK calls
+};
+
+export const MOCK_DB = {
+  get(path) { return state.docs.has(path) ? clone(state.docs.get(path)) : null; },
+  set(path, data) {
+    state.docs.set(path, clone(data));
+    this._notify(path);
+  },
+  merge(path, patch) {
+    const cur = state.docs.has(path) ? state.docs.get(path) : {};
+    const next = { ...cur, ...clone(patch) };
+    state.docs.set(path, next);
+    this._notify(path);
+  },
+  delete(path) {
+    state.docs.delete(path);
+    this._notify(path);
+  },
+  collection(collPath) {
+    const out = [];
+    for (const [p, data] of state.docs) {
+      const parent = p.split('/').slice(0, -1).join('/');
+      if (parent === collPath) out.push({ id: p.split('/').pop(), data: clone(data) });
+    }
+    return out;
+  },
+  subscribe(path, cb) {
+    if (!state.subscribers.has(path)) state.subscribers.set(path, new Set());
+    state.subscribers.get(path).add(cb);
+    return () => state.subscribers.get(path)?.delete(cb);
+  },
+  _notify(path) {
+    // notify exact doc path subscribers
+    if (state.subscribers.has(path)) state.subscribers.get(path).forEach(cb => cb());
+    // notify parent collection subscribers
+    const parent = path.split('/').slice(0, -1).join('/');
+    if (parent && state.subscribers.has(parent)) state.subscribers.get(parent).forEach(cb => cb());
+  },
+  nextId() { state.counter += 1; return String(state.counter).padStart(3, '0'); },
+  _state: state,
+};
+
+export function recordCall(entry) {
+  state.calls.push({ ...entry, ts: Date.now() });
+}
+
+export function resetMockDb() {
+  state.docs.clear();
+  state.subscribers.clear();
+  state.calls.length = 0;
+  state.counter = 0;
+}
+
+export function getCalls() {
+  return [...state.calls];
+}
+
+function clone(v) {
+  if (v === null || v === undefined) return v;
+  return JSON.parse(JSON.stringify(v));
+}