S allius/issue387 (#388)

* add optional java script to fetch data regullary

* change file extension to `html.j2` for templates

* fix route for fetch data

- for running in iframes (e.g. HA ingress) we must
  use relative path in the URLs

* increase test coverage

* remove unused statements

app/translations/de/LC_MESSAGES/messages.po

@@ -8,7 +8,7 @@ msgid ""
 msgstr ""
 "Project-Id-Version: tsun-gen3-proxy 0.14.0\n"
 "Report-Msgid-Bugs-To: EMAIL@ADDRESS\n"
-"POT-Creation-Date: 2025-04-18 20:46+0200\n"
+"POT-Creation-Date: 2025-04-20 00:01+0200\n"
 "PO-Revision-Date: 2025-04-18 16:24+0200\n"
 "Last-Translator: FULL NAME <EMAIL@ADDRESS>\n"
 "Language: de\n"
@@ -19,7 +19,7 @@ msgstr ""
 "Content-Transfer-Encoding: 8bit\n"
 "Generated-By: Babel 2.17.0\n"
 
-#: src/web/templates/index.html:5
+#: src/web/templates/index.html.j2:5
 msgid "My Dashboard"
 msgstr "Mein Dashboard"