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

docker-compose.yml

@@ -0,0 +1,52 @@
+services:
+  node1:
+    build: .
+    command:
+      - "--addr"
+      - "172.20.0.11:8080"
+      - "--peer"
+      - "172.20.0.12:8080"
+      - "--peer"
+      - "172.20.0.13:8080"
+    networks:
+      cluster:
+        ipv4_address: 172.20.0.11
+    ports:
+      - "8081:8080"
+
+  node2:
+    build: .
+    command:
+      - "--addr"
+      - "172.20.0.12:8080"
+      - "--peer"
+      - "172.20.0.11:8080"
+      - "--peer"
+      - "172.20.0.13:8080"
+    networks:
+      cluster:
+        ipv4_address: 172.20.0.12
+    ports:
+      - "8082:8080"
+
+  node3:
+    build: .
+    command:
+      - "--addr"
+      - "172.20.0.13:8080"
+      - "--peer"
+      - "172.20.0.11:8080"
+      - "--peer"
+      - "172.20.0.12:8080"
+    networks:
+      cluster:
+        ipv4_address: 172.20.0.13
+    ports:
+      - "8083:8080"
+
+networks:
+  cluster:
+    driver: bridge
+    ipam:
+      config:
+        - subnet: 172.20.0.0/24