Give every JSON answer @meta, errors included (closes #201)

A panic in a JSON route's handler answered 500 with an empty body,
because the router's recoverer sits outside the middleware that adds
`@meta`. `JSONValidationMiddleware` now wraps the handler in the same
recoverer, and answers the panic with the JSON error body.

`/status.json` and the health check answered chi's empty 405 to any
method they do not take. They now answer with the same JSON 405 as the
routes under `/api/v1` and `/ip`.

The home page's IP lookup card showed only the answer's `data`. It now
shows the whole answer, `@meta` included.

A table test checks `@meta` on every JSON route, in its successes and
its errors.

Model: opus-5-5

internal/server/routes.go

@@ -8,8 +8,8 @@ import (
 	"github.com/go-chi/chi/v5/middleware"
 )
 
-// The error messages the JSON routes under /api/v1 and /ip answer with when no
-// route matches the path, and when none takes the method.
+// The error messages the JSON routes answer with when no route matches the
+// path, and when the route does not take the method.
 const (
 	notFoundMessage         = "Not found"
 	methodNotAllowedMessage = "Method not allowed"
@@ -19,6 +19,13 @@ const (
 	jsonRoutesAllow = "GET, HEAD"
 )
 
+// The paths of the status figures and the health check, the two JSON routes
+// outside /api/v1 and /ip.
+const (
+	statusJSONPath  = "/status.json"
+	healthCheckPath = "/.well-known/healthcheck.json"
+)
+
 // setupRoutes configures the HTTP routes
 func (s *Server) setupRoutes() {
 	r := chi.NewRouter()
@@ -32,6 +39,8 @@ func (s *Server) setupRoutes() {
 	r.Use(middleware.RequestID)
 	r.Use(RealIPMiddleware(s.trustedProxies))
 	r.Use(RequestLoggerMiddleware(s.logger.Logger)) // Structured request logging
+	// Recoverer answers a panic on a page. JSONValidationMiddleware recovers a
+	// panic on a JSON route itself, so that the answer is JSON with @meta.
 	r.Use(middleware.Recoverer)
 	r.Use(JSONResponseMiddleware)
 	// Timeout must come after JSONResponseMiddleware, which sends its answer
@@ -43,11 +52,6 @@ func (s *Server) setupRoutes() {
 	// Routes
 	r.Get("/", s.handleIndex())
 	r.Get("/status", s.handleStatusHTML())
-	r.Get("/status.json", JSONValidationMiddleware(s.handleStatusJSON()).ServeHTTP)
-	r.Get(
-		"/.well-known/healthcheck.json",
-		JSONValidationMiddleware(s.handleHealthCheck()).ServeHTTP,
-	)
 
 	// AS and prefix detail pages
 	r.Get("/as/{asn}", s.handleASDetail())
@@ -70,6 +74,21 @@ func (s *Server) setupRoutes() {
 		s.writeJSONError(w, http.StatusMethodNotAllowed, methodNotAllowedMessage)
 	}
 
+	// The status figures and the health check. chi sets one 405 answer for a
+	// whole router. These two routes are on the pages' router, whose 405 stays
+	// chi's own. So each method they do not take is routed to the JSON 405
+	// here.
+	r.Get(statusJSONPath, JSONValidationMiddleware(s.handleStatusJSON()).ServeHTTP)
+	r.Get(healthCheckPath, JSONValidationMiddleware(s.handleHealthCheck()).ServeHTTP)
+
+	for _, method := range []string{
+		http.MethodPost, http.MethodPut, http.MethodPatch, http.MethodDelete,
+		http.MethodOptions, http.MethodTrace, http.MethodConnect,
+	} {
+		r.MethodFunc(method, statusJSONPath, jsonMethodNotAllowed)
+		r.MethodFunc(method, healthCheckPath, jsonMethodNotAllowed)
+	}
+
 	// IP info JSON endpoints (replaces old /ip redirect)
 	r.Route("/ip", func(r chi.Router) {
 		r.Use(JSONValidationMiddleware)