Since the laika frontend renders client-side we don't need a full templating engine anymore.
**Acceptance criteria**
* Replace Twig with a class that collects the variables similar to Twig and outputs them into the data attribute in the Vue mount point.
* Automatically map routes to JS entry points (replacing the individual JavaScript tags in current Twig templates).
* Replace unit test checks that check for a specific output with checks that look for specific assignments in the template context.
**Notes**
* The Twig template engine is still used in email templates.
* Unit (and edge-to-edge) tests need to be changed, as some of them are checking template output that use some test templates.
* Tests for the address change feature parses data attributes of the output.
* Looking at the class `TwigTemplate` might help understanding what's required.
**Possible Solution**
* Introduce implementation of the interface `Template` that has the methods `render()` and `assign()`.
* Replace context array by calls to `assign()`.
* Mapping the routes can happen in `Template::render()`.
* The `Template` implementation can have a `getAssignedVariables()` method to also be used in unit tests.
* Go through all calls of `getLayoutTemplate()` and replace by `getNewLayoutTemplate()` making sure that unit tests still pass or are fixed respectively.