Ask for server URL before showing sign in box

Contact the server's .well-known API before anything to get
available login flows instead of blindly assuming it will be
m.login.password, and to get the server's real URL instead of
requiring users to remember that e.g. it's "chat.privacytools.io"
and not just "privacytools.io" despite user IDs making it look like so.

The server field will also now remember the last accepted URL.

src/icons/thin/server-connect.svg

@@ -0,0 +1,3 @@
+<svg height="24" viewBox="0 0 24 24" width="24" xmlns="http://www.w3.org/2000/svg">
+    <path d="m12 0c-6.627 0-12 5.373-12 12s5.373 12 12 12 12-5.373 12-12-5.373-12-12-12zm5.73 20.183c-.106-.526-.236-1.046-.398-1.555.897-.811.86-2.197-.072-2.883.582-2.318.61-4.849-.002-7.288.186-.111.348-.254.475-.425 1.466.412 2.831 1.066 4.052 1.911.14.665.215 1.352.215 2.057 0 3.382-1.692 6.372-4.27 8.183zm-15.73-8.183c0-.855.12-1.682.323-2.475.699-.044 1.393-.04 2.147.032l.04.226c-.921.775-1.75 1.661-2.487 2.674zm3.183-1.19c.848.643 2.083.436 2.662-.49 2.898 1.06 5.339 3.077 6.94 5.666-.766.775-.756 1.998.019 2.695-.681 1.231-1.548 2.345-2.56 3.307-4.902.117-8.924-3.262-9.969-7.697.772-1.316 1.755-2.494 2.908-3.481zm2.886-1.901c1.991-.974 4.155-1.432 6.324-1.377.305.611.93 1.076 1.666 1.166h.006c.557 2.157.583 4.472.029 6.7l-.223.023c-1.724-2.825-4.433-5.131-7.763-6.301zm6.062 12.857c.702-.817 1.311-1.695 1.813-2.627l.27-.008c.172.562.308 1.139.408 1.729-.777.406-1.612.714-2.491.906zm7.103-13.598c-1.009-.56-2.076-1.002-3.189-1.311-.108-.995-1.041-1.824-2.119-1.816-.552-1.019-1.232-1.975-2.024-2.854 3.321.642 6.061 2.93 7.332 5.981zm-6.472-2.708c-.257.22-.443.515-.524.858-2.456-.03-4.778.526-6.848 1.565-.85-.638-2.07-.421-2.646.483-.728-.076-1.379-.092-2.024-.072 1.476-3.683 5.076-6.294 9.28-6.294h.001c1.097.994 2.034 2.16 2.761 3.46z"/>
+</svg>

src/icons/thin/sign-in-insecure.svg

@@ -0,0 +1,3 @@
+<svg height="24" viewBox="0 0 24 24" width="24" xmlns="http://www.w3.org/2000/svg">
+    <path d="m8 9v-3c0-2.206 1.794-4 4-4s4 1.794 4 4v3h2v-3c0-3.313-2.687-6-6-6s-6 2.687-6 6v3zm.746 2h2.831l-8.577 8.787v-2.9zm12.254 1.562v-1.562h-1.37l-12.69 13h2.894zm-6.844-1.562-11.156 11.431v1.569h1.361l12.689-13zm6.844 7.13v-2.927l-8.586 8.797h2.858zm-3.149 5.87h3.149v-3.226zm-11.685-13h-3.166v3.244z"/>
+</svg>

src/icons/thin/sign-in-local-http.svg

@@ -0,0 +1,3 @@
+<svg height="24" viewBox="0 0 24 24" width="24" xmlns="http://www.w3.org/2000/svg">
+    <path d="m8 9v-3c0-2.206 1.794-4 4-4s4 1.794 4 4v3h2v-3c0-3.313-2.687-6-6-6s-6 2.687-6 6v3zm.746 2h2.831l-8.577 8.787v-2.9zm12.254 1.562v-1.562h-1.37l-12.69 13h2.894zm-6.844-1.562-11.156 11.431v1.569h1.361l12.689-13zm6.844 7.13v-2.927l-8.586 8.797h2.858zm-3.149 5.87h3.149v-3.226zm-11.685-13h-3.166v3.244z"/>
+</svg>

src/icons/thin/sign-in-secure.svg

@@ -0,0 +1,3 @@
+<svg height="24" viewBox="0 0 24 24" width="24" xmlns="http://www.w3.org/2000/svg">
+    <path d="m21 21v3h-18v-3zm-13-15c0-2.206 1.795-4 4-4s4 1.794 4 4v3h2v-3c0-3.313-2.687-6-6-6s-6 2.687-6 6v3h2zm13 8v-3h-18v3zm0 5v-3h-18v3z"/>
+</svg>