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>

Dockerfile

@@ -1,15 +1,20 @@
-FROM golang:1.24-alpine AS builder
+FROM golang:1.25-alpine AS builder
+
+ARG VERSION=dev
 
 WORKDIR /build
 COPY go.mod go.sum ./
 RUN go mod download
 COPY . .
-RUN CGO_ENABLED=0 go build -trimpath -ldflags="-s -w" -o mc-proxy ./cmd/mc-proxy
+RUN CGO_ENABLED=0 go build -trimpath -ldflags="-s -w -X main.version=${VERSION}" \
+    -o mc-proxy ./cmd/mc-proxy
 
 FROM alpine:3.21
 
 RUN addgroup -S mc-proxy && adduser -S mc-proxy -G mc-proxy
+
 COPY --from=builder /build/mc-proxy /usr/local/bin/mc-proxy
 
 USER mc-proxy
 ENTRYPOINT ["mc-proxy"]
+CMD ["server", "--config", "/srv/mc-proxy/mc-proxy.toml"]