feat(web): initial implementation — server, mw, httputil, health (v1.0.0)

Introduces code.nochebuena.dev/einherjar/web — the HTTP transport layer of the
Einherjar framework. Absorbs httpserver, httpmw, and httputil from micro-lib,
replacing gorilla/mux with chi, adopting SecurityBag-native middleware, and
centralizing error handling through a single httputil.Error function.

server:
- Server interface — embeds lifecycle.Component and chi.Router
- Config struct (EINHERJAR_SERVER_* env vars); DefaultConfig
- New(logger, cfg, opts...) Server; WithMiddleware option
- Binds TCP synchronously in OnStart; logs "server: listening" on success
- Graceful shutdown within ShutdownTimeout on OnStop

mw:
- Recover — catches panics, returns 500, logs at Error
- RequestID — injects UUID v7 (UUID v4 fallback) into context and X-Request-ID header
- RequestLogger — structured access log per request
- CORS / CORSAllowAll — chi-based, applied only when origins non-empty
- IPRateLimit / UserRateLimit — pluggable RateLimiterStore interface
- InMemoryRateLimiterStore — token-bucket backed by golang.org/x/time/rate;
  background goroutine evicts stale entries every 5 minutes
- StatusRecorder — wraps ResponseWriter to capture HTTP status code

httputil:
- Handle[Req, Res] / HandleNoBody[Res] / HandleEmpty[Req] — generic handler adapters
- Error(logger, w, r, err) — derives log level from status (≥500→Error, 4xx→Warn,
  499→Info); writes standardized JSON body; logz enriches *xerrors.Err automatically
- JSON(w, status, v) / NoContent(w) — response helpers
- HandlerFunc adapter type

health:
- NewHandler / NewHandlerWithConfig — runs all Checkable checks concurrently;
  returns JSON {status, components} with per-component latency and error
- Config struct (EINHERJAR_HEALTH_CHECK_TIMEOUT, default 5s)

Root factory:
- web.New(logger, cfg...) Server — composes Recover+RequestID+RequestLogger+CORS
  in outermost-first order; CORS applied only when AllowedOrigins non-empty

- server.Server interface and web/server/identifiable.go: embeds observability.Identifiable;
  ModulePath and ModuleVersion read via runtime/debug.ReadBuildInfo() — prints in launcher banner

mw/doc.go

@@ -0,0 +1,24 @@
+// Package mw provides transport-level HTTP middleware for Einherjar services.
+//
+// All middleware functions return func(http.Handler) http.Handler and are
+// composed via [server.WithMiddleware] or chi's Use method.
+//
+// # Recommended middleware order (outermost first)
+//
+//	server.WithMiddleware(
+//	    mw.Recover(),
+//	    mw.RequestID(uuid.NewString),
+//	    mw.RequestLogger(logger),
+//	    mw.CORS([]string{"https://example.com"}),
+//	)
+//
+// # Rate limiting
+//
+//	// In-memory (default — no extra dependencies)
+//	store := mw.NewInMemoryRateLimiterStore(100, 20)
+//	srv.Use(mw.IPRateLimit(store, logger))
+//
+//	// Distributed — swap store, middleware unchanged
+//	store := valkeymw.NewRateLimiterStore(client, 100, 20)
+//	srv.Use(mw.IPRateLimit(store, logger))
+package mw