(core) move client code to core

Summary:
This moves all client code to core, and makes minimal fix-ups to
get grist and grist-core to compile correctly.  The client works
in core, but I'm leaving clean-up around the build and bundles to
follow-up.

Test Plan: existing tests pass; server-dev bundle looks sane

Reviewers: dsagal

Reviewed By: dsagal

Differential Revision: https://phab.getgrist.com/D2627

app/client/ui/CustomThemes.ts

@@ -0,0 +1,59 @@
+import {GristLoadConfig} from 'app/common/gristUrls';
+import {styled} from 'grainjs';
+
+export type ProductFlavor = 'grist' | 'efcr' | 'fieldlink';
+
+export interface CustomTheme {
+  bodyClassName?: string;
+  wideLogo?: boolean;   // Stretch the logo and hide the org name.
+}
+
+export function getFlavor(org?: string): ProductFlavor {
+  // Using a URL parameter e.g. __themeOrg=fieldlink allows overriding the org used for custom
+  // theming, for testing.
+  const themeOrg = new URLSearchParams(window.location.search).get('__themeOrg');
+  if (themeOrg) { org = themeOrg; }
+
+  if (!org) {
+    const gristConfig: GristLoadConfig = (window as any).gristConfig;
+    org = gristConfig && gristConfig.org;
+  }
+  if (org === 'fieldlink') {
+    return 'fieldlink';
+  } else if (org && /^nioxus(-.*)?$/.test(org)) {
+    return 'efcr';
+  }
+  return 'grist';
+}
+
+export function getTheme(flavor: ProductFlavor): CustomTheme {
+  switch (flavor) {
+    case 'fieldlink':
+      return {
+        wideLogo: true,
+        bodyClassName: cssFieldLinkBody.className,
+      };
+    case 'efcr':
+      return {bodyClassName: cssEfcrBody.className};
+    default:
+      return {};
+  }
+}
+
+const cssEfcrBody = styled('body', `
+  --icon-GristLogo: url("icons/logo-efcr.png");
+  --grist-logo-bg: #009975;
+  --grist-color-light-green: #009975;
+  --grist-color-dark-green: #007F61;
+  --grist-primary-fg: #009975;
+  --grist-primary-fg-hover: #007F61;
+  --grist-control-fg: #009975;
+  --grist-color-darker-green: #004C38;
+  --grist-color-dark-bg: #004C38;
+`);
+
+const cssFieldLinkBody = styled('body', `
+  --icon-GristLogo: url("icons/logo-fieldlink.png");
+  --icon-GristWideLogo: url("icons/logo-fieldlink.png");
+  --grist-logo-bg: white;
+`);