maybe actually fix hcaptcha

src/webapp/api.v

···
 	// before doing *anything*, check the captchas
 	if app.config.hcaptcha.enabled {
 		token := ctx.form['h-captcha-response']
-		response := http.post_json('https://api.hcaptcha.com/siteverify', '{
-			"secret": "${app.config.hcaptcha.secret}",
-			// "remoteip": "${ctx.ip()}",
-			"response": "${token}"
-		}') or {
+		response := http.post_form('https://api.hcaptcha.com/siteverify', {
+			'secret':   app.config.hcaptcha.secret
+			'remoteip': ctx.ip()
+			'response': token
+		}) or {
 			ctx.error('failed to post hcaptcha response: ${err}')
 			return ctx.redirect('/register')
 		}