Add documentation, Docker setup, and tests for server and gRPC packages

Rewrite README with project overview and quick start. Add RUNBOOK with
operational procedures and incident playbooks. Fix Dockerfile for Go 1.25
with version injection. Add docker-compose.yml. Clean up golangci.yaml
for mc-proxy. Add server tests (10) covering the full proxy pipeline with
TCP echo backends, and grpcserver tests (13) covering all admin API RPCs
with bufconn and write-through DB verification.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

deploy/docker/docker-compose.yml

@@ -0,0 +1,14 @@
+services:
+  mc-proxy:
+    build:
+      context: ../..
+      dockerfile: Dockerfile
+      args:
+        VERSION: "${VERSION:-dev}"
+    ports:
+      - "443:443"
+      - "8443:8443"
+      - "9443:9443"
+    volumes:
+      - /srv/mc-proxy:/srv/mc-proxy
+    restart: unless-stopped