Implement basic login function; add basic styling

public/static/style.css

@@ -0,0 +1,50 @@
+html, body {
+    max-width: 100%;
+    margin: 0;
+    padding: 0;
+}
+
+* {
+    box-sizing: border-box;
+}
+
+body {
+    font-family: sans-serif;
+}
+
+/* --- Header --- */
+header {
+    margin: 1em;
+}
+
+header h1 {
+    margin: 1em;
+}
+
+/* --- Login page --- */
+main.login_page {
+    margin: 2em;
+    padding: 1em;
+    border: 1px gray solid;
+    width: auto;
+}
+
+main.login_page h2 {
+    margin: 0 0 0.5em 0;
+}
+
+main.login_page table td {
+    padding: 0.2em;
+}
+
+/* --- Text and other styling --- */
+.error {
+    background: #ff4444;
+    width: 30em;
+    margin: 1em 0;
+    padding: 1em;
+}
+
+button {
+    padding: 0.2em 1em;
+}