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_internal_test.go

@@ -17,7 +17,7 @@ func TestRoutesAnswerHEAD(t *testing.T) {
 
 	s := newServerWithTestRoutes(t)
 
-	for _, path := range []string{"/", statsPath, "/ip", "/ip/"} {
+	for _, path := range []string{"/", statusJSONPath, statsPath, "/ip", "/ip/"} {
 		rec := httptest.NewRecorder()
 		s.router.ServeHTTP(rec, httptest.NewRequestWithContext(
 			t.Context(), http.MethodHead, path, nil))
@@ -31,10 +31,13 @@ func TestRoutesAnswerHEAD(t *testing.T) {
 
 // TestJSONRoutesAnswerUnmatchedRequestsWithJSONErrors sends a method the JSON
 // routes do not take, and a path none of them matches, to each group of JSON
-// routes through the server's router. Each must answer with the JSON error
+// routes through the server's router. It also sends a method they do not take
+// to /status.json and the health check. Each must answer with the JSON error
 // body, and a 405 must name the methods the routes take in its Allow header.
 // Before the fix a 405 said "Internal server error" and a 404 was chi's plain
 // text answer (https://git.eeqj.de/sneak/routewatch/issues/111).
+// /status.json and the health check gave chi's empty 405
+// (https://git.eeqj.de/sneak/routewatch/issues/201).
 func TestJSONRoutesAnswerUnmatchedRequestsWithJSONErrors(t *testing.T) {
 	t.Parallel()
 
@@ -48,6 +51,14 @@ func TestJSONRoutesAnswerUnmatchedRequestsWithJSONErrors(t *testing.T) {
 	}{
 		{http.MethodPost, statsPath, http.StatusMethodNotAllowed, methodNotAllowedMessage},
 		{http.MethodPost, "/ip/", http.StatusMethodNotAllowed, methodNotAllowedMessage},
+		{
+			http.MethodDelete, statusJSONPath,
+			http.StatusMethodNotAllowed, methodNotAllowedMessage,
+		},
+		{
+			http.MethodOptions, healthCheckPath,
+			http.StatusMethodNotAllowed, methodNotAllowedMessage,
+		},
 		{http.MethodGet, "/api/v1/nothing", http.StatusNotFound, notFoundMessage},
 		{http.MethodGet, "/ip/192.0.2.1/nothing", http.StatusNotFound, notFoundMessage},
 	}