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

httputil/handle.go

@@ -0,0 +1,73 @@
+package httputil
+
+import (
+	"context"
+	"encoding/json"
+	"net/http"
+
+	"code.nochebuena.dev/einherjar/contracts/logging"
+	"code.nochebuena.dev/einherjar/core/valid"
+	"code.nochebuena.dev/einherjar/core/xerrors"
+)
+
+// Handle adapts a typed business function to http.HandlerFunc.
+//   - Decodes the JSON request body into Req.
+//   - Validates Req using the provided [valid.Validator].
+//   - Calls fn with the request context and decoded Req.
+//   - Encodes Res as JSON with HTTP 200 on success.
+//   - On error: logs via [Error] (level derived from HTTP status) and writes the standardized JSON body.
+func Handle[Req, Res any](v valid.Validator, logger logging.Logger, fn func(ctx context.Context, req Req) (Res, error)) http.HandlerFunc {
+	return func(w http.ResponseWriter, r *http.Request) {
+		var req Req
+		if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
+			Error(logger, w, r, xerrors.New(xerrors.ErrInvalidInput, "invalid JSON: "+err.Error()))
+			return
+		}
+		if err := v.Struct(req); err != nil {
+			Error(logger, w, r, err)
+			return
+		}
+		res, err := fn(r.Context(), req)
+		if err != nil {
+			Error(logger, w, r, err)
+			return
+		}
+		JSON(w, http.StatusOK, res)
+	}
+}
+
+// HandleNoBody adapts a typed function with no request body (GET, HEAD).
+// Calls fn with the request context; encodes the result as JSON with HTTP 200.
+// On error: logs via [Error] and writes the standardized JSON body.
+func HandleNoBody[Res any](logger logging.Logger, fn func(ctx context.Context) (Res, error)) http.HandlerFunc {
+	return func(w http.ResponseWriter, r *http.Request) {
+		res, err := fn(r.Context())
+		if err != nil {
+			Error(logger, w, r, err)
+			return
+		}
+		JSON(w, http.StatusOK, res)
+	}
+}
+
+// HandleEmpty adapts a typed function with a request body but no response body.
+// Decodes and validates Req, calls fn, returns 204 No Content on success.
+// On error: logs via [Error] and writes the standardized JSON body.
+func HandleEmpty[Req any](v valid.Validator, logger logging.Logger, fn func(ctx context.Context, req Req) error) http.HandlerFunc {
+	return func(w http.ResponseWriter, r *http.Request) {
+		var req Req
+		if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
+			Error(logger, w, r, xerrors.New(xerrors.ErrInvalidInput, "invalid JSON: "+err.Error()))
+			return
+		}
+		if err := v.Struct(req); err != nil {
+			Error(logger, w, r, err)
+			return
+		}
+		if err := fn(r.Context(), req); err != nil {
+			Error(logger, w, r, err)
+			return
+		}
+		NoContent(w)
+	}
+}