Bump Docker base images to node 22; mock firestore comment cleanup

Both Dockerfiles (root firebase-mode + docker/ caddy) bumped node:18-alpine
to node:22-alpine. better-sqlite3 v12 (from PR #6) requires node 20+; node 18
builds fail with node-gyp/python errors. openssl-legacy-provider flag kept
for react-scripts 5 compat.

.dockerignore: removed .env* exclusion so .env.local COPY works in firebase
image build.

mock firestore applyConstraints comment: offset handled by adapter (firebase.js
slices), mock never sees it — clarified dead-code reasoning.

src/__mocks__/firebase/firestore.js

@@ -105,9 +105,9 @@ export function onSnapshot(refOrQuery, onSuccess, onError) {
   return unsub;
 }
 
-// Apply Firestore-style query constraints (orderBy desc/asc, limit) to mock docs.
-// Mirrors real SDK semantics enough for contract tests. Only orderBy + limit
-// supported (App's LOG_QUERY uses exactly these).
+// Apply Firestore-style query constraints (orderBy desc/asc, limit, where)
+// to mock docs. Mirrors real SDK semantics for contract tests. Offset handled
+// by adapter (firebase.js slices) — mock never sees it.
 function applyConstraints(docs, constraints) {
   let out = [...docs];
   for (const c of constraints) {