🔒 fix: exclude .env from Docker context and git

Dockerfile runs COPY . . and Docker does not read .gitignore. This
repo takes config via runtime env vars and has no .env today, but
nothing prevented one from being created (e.g. for local compose use),
committed, or baked into an image layer. Cheap insurance on both
fronts.

Author: luiscosio

.dockerignore

@@ -4,3 +4,5 @@ node_modules
 npm-debug.log*
 test-results
 traces-*.json
+.env
+.env.*

.gitignore

@@ -1,3 +1,5 @@
 node_modules/
 test-results/
 traces-*.json
+.env
+.env.*