Add library build, Docker cluster, and example client

Introduce a Makefile that builds libtoastyfs.a and libtoastyfs.so from the
client-side sources (client, tcp, byte_queue, message, basic) so external
programs can link against the ToastyFS client API in include/toastyfs.h.

Add a Dockerfile and docker-compose.yml that spin up a 3-node ToastyFS
server cluster on a private bridge network with ports 8081-8083 exposed
on the host. Include cluster.sh as a convenience wrapper (up/down/status/
logs/run) — the "run" sub-command builds the library, compiles a user-
supplied C source against it, starts the cluster, and executes the binary.

Add examples/example.c demonstrating synchronous PUT, GET, DELETE, and a
NOT_FOUND verification.

https://claude.ai/code/session_019DVhmc25jfzcHnmdNxzib2

.gitignore

@@ -6,4 +6,8 @@ toastyfs_simulation
 *.gcov
 *.info
 coverage_html/
-*.log
+*.log
+*.o
+*.a
+*.so
+examples/example