Remove fomantic form module

[silverwind]

• Replace fomantic form CSS with custom module
• Moved code in form.css to modules/form.css, removed around 70% of the previous module.
• Moved captcha styles previously in form.css to its own file.

There is probably more unused CSS, like form error state colors which to my knowledge is not used anywhere, but I'm not sure about that one so I kept it.

One notable change is the removal of type combinator here, which lowers the selector specificity and I noticed one issue where selector .ui.search > .prompt was winning, so I added a workaround for that until the search module can be removed as well.

.ui.form .fields.error .field input:not([type])
.ui.form .fields.error .field input[type="date"]