feat: ja4-platform monorepo — 5 services unified, tests & RPM builds standardized

Services:
- ja4sentinel: TLS/JA4 fingerprint capture daemon (Go, libpcap)
- logcorrelator: JA4 log correlation engine (Go, ClickHouse)
- mod_reqin_log: Apache module (C, JSON request logging)
- bot_detector: ML bot detection pipeline (Python)
- dashboard: FastAPI/Streamlit analytics UI (Python)

Shared libraries:
- shared/go/ja4common: logger, config, shutdown, ipfilter (Go module)
- shared/python/ja4_common: ClickHouseClient, ClickHouseSettings (Python package)
- shared/clickhouse/: canonical SQL migrations (10 files)

Build & packaging:
- Unified 3-stage Dockerfile.package for Go RPMs (el8/el9/el10)
- go.work workspace linking sentinel, correlator, ja4common
- Makefile with test-all, build-all, rpm-* targets

Fixes applied:
- go.work: 1.21 → 1.24.6 (required by sentinel)
- correlator Dockerfiles: golang:1.21 → golang:1.24
- replace directives in go.mod for ja4common local path
- pyproject.toml: setuptools.backends → setuptools.build_meta
- Removed static libpcap linking (unavailable on Rocky 9)
- Fixed data races in output/writers_test.go (sync.Mutex + atomic.Int32)
- Rewrote corrupted test files (logger_test.go × 2)

Test coverage:
- correlator: 67.1% total (unixsocket 80.5%, config 91.7%, app 83.3%, multi 87.7%, stdout 100%)
- sentinel: all 10 packages pass (api, capture, config, fingerprint, ipfilter, logging, output, tlsparse)

Documentation:
- README.md + docs/ (architecture, development, 5 services, shared libs, DB schema & migrations)

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

shared/go/ja4common/shutdown/handler.go

@@ -0,0 +1,45 @@
+// Package shutdown provides graceful shutdown handling for services.
+package shutdown
+
+import (
+	"context"
+	"os"
+	"os/signal"
+	"syscall"
+)
+
+// Hook is a cleanup function called during shutdown.
+type Hook struct {
+	Name string
+	Fn   func() error
+}
+
+// simpleLogger is the minimal interface required from a logger.
+type simpleLogger interface {
+	Info(string)
+	Error(string, error)
+}
+
+// Handle blocks until SIGTERM or SIGINT is received, then cancels the context
+// and runs hooks in order. Each hook error is logged but does not abort remaining hooks.
+func Handle(ctx context.Context, cancel context.CancelFunc, hooks []Hook, logger simpleLogger) {
+	quit := make(chan os.Signal, 1)
+	signal.Notify(quit, syscall.SIGTERM, syscall.SIGINT)
+	defer signal.Stop(quit)
+
+	select {
+	case sig := <-quit:
+		logger.Info("shutdown signal received: " + sig.String())
+	case <-ctx.Done():
+		logger.Info("context cancelled, shutting down")
+	}
+
+	cancel()
+
+	for _, h := range hooks {
+		logger.Info("running shutdown hook: " + h.Name)
+		if err := h.Fn(); err != nil {
+			logger.Error("shutdown hook "+h.Name+" failed", err)
+		}
+	}
+}