chore: project skeleton + phase-1 plan

.gitignore

@@ -0,0 +1,27 @@
+# Elixir/Mix
+/server/_build/
+/server/deps/
+/server/cover/
+/server/doc/
+/server/.fetch
+/server/erl_crash.dump
+/server/*.ez
+/server/priv/static/assets/
+/server/priv/static/cache_manifest.json
+/server/*.db
+/server/*.db-journal
+/server/*.db-wal
+/server/*.db-shm
+
+/agent/_build/
+/agent/deps/
+/agent/cover/
+/agent/doc/
+/agent/.fetch
+/agent/erl_crash.dump
+/agent/*.ez
+
+# Editors / OS
+.DS_Store
+.vscode/
+.idea/