v4: every email is rendered by its template in api/mail/ on one layout that takes the instance's style, and sent one way — the welcome email was built and sent inside the register route and the reset link in its service, each writing Markdown, running marked, and calling a nodemailer wrapper whose cc, bcc, replyTo and send result nothing used. Now api/mail/ holds one template per email (welcome.ts, password-reset.ts) on layout.ts's EmailKit, which draws each block with inline styles in a style from styles.ts: the six site styles' palettes, copied from src/themes/, and what makes each recognisable in a mail client (Brutalist's hard border and shadow, GeoCities' ridge and rainbow rules, Times' underlined ink links, Kanagawa's colored quotes, dates and wordmark, Melange's spice bar). On the "auto" scheme the light palette is inlined and the dark one swapped in by a prefers-color-scheme block; a chosen scheme sends only its own. User-written text is escaped where it lands. strings.ts holds every email's words in English and French. GERBEUR_EMAIL_LOCALE picks the language and GERBEUR_DEFAULT_STYLE the instance's style, which the welcome and reset emails are drawn in; GERBEUR_WELCOME_EMAIL_BODY still replaces the welcome's Markdown, whose blocks now take the style too. email-service sends a rendered email with its recipient and headers, refuses to load when GERBEUR_SMTPS_URL is set without GERBEUR_FROM_EMAIL (sends used to fail one by one), and takes a test transport, through which the tests now read what was sent. The welcome send moves to user-service's sendWelcomeEmail. The style and scheme names move to shared/theme.ts, which the server now needs. README, mod.ts and .env.example describe mail/ and the new variables, and drop the "notifications, invites" email that never existed. 221 backend tests pass (new: the layout's schemes, styles and escaping, both templates, the welcome on sign-up, a reset link from the email that works), and deno check, deno lint, doc:lint, deno fmt, tsc and eslint are clean.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

api/config.ts

@@ -7,33 +7,50 @@
  * @module
  */
 
+import { isStyleName, type StyleName } from "../shared/theme.ts";
+
 /** The port the server listens on (`GERBEUR_PORT`, default 8000). */
 export const PORT: number = Number(Deno.env.get("GERBEUR_PORT")) || 8000;
 /**
- * The `smtps://` URL of the server email-service sends mail through
- * (`GERBEUR_SMTPS_URL`). When it is empty, the welcome and password reset
- * emails are silently skipped.
+ * The `smtps://` URL of the server `email-service.ts` sends mail through
+ * (`GERBEUR_SMTPS_URL`). When it is empty, no email is sent: sign-up sends no
+ * welcome, a password reset request does nothing, and there are no digests.
  */
 export const SMTPS_URL: string = Deno.env.get("GERBEUR_SMTPS_URL")?.trim() ||
   "";
-/** The `From` address of the welcome and password reset emails. */
+/**
+ * The `From` address of every email (`GERBEUR_FROM_EMAIL`), as an address or
+ * as `Name <address>`. `email-service.ts` refuses to load without it when
+ * {@link SMTPS_URL} is set.
+ */
 export const FROM_EMAIL: string = Deno.env.get("GERBEUR_FROM_EMAIL")?.trim() ||
   "";
-
-const DEFAULT_WELCOME_EMAIL_BODY = `# Welcome to {{site_name}}!
-
-Hi **{{username}}**,
-
-Your account has been created successfully. Welcome aboard!`;
-
 /**
  * The Markdown of the welcome email sent on registration
- * (`GERBEUR_WELCOME_EMAIL_BODY`). The users route replaces `{{site_name}}` and
- * `{{username}}` in it and sends it as both text and HTML.
+ * (`GERBEUR_WELCOME_EMAIL_BODY`), or null for the built-in one in the
+ * {@link EMAIL_LOCALE}. `api/mail/welcome.ts` replaces `{{site_name}}` and
+ * `{{username}}` in it.
  */
-export const WELCOME_EMAIL_BODY: string =
-  Deno.env.get("GERBEUR_WELCOME_EMAIL_BODY")?.trim() ||
-  DEFAULT_WELCOME_EMAIL_BODY;
+export const WELCOME_EMAIL_BODY: string | null =
+  Deno.env.get("GERBEUR_WELCOME_EMAIL_BODY")?.trim() || null;
+/** A language the emails are written in. */
+export type EmailLocale = "en" | "fr";
+/**
+ * The language of every email (`GERBEUR_EMAIL_LOCALE`). The interface picks
+ * each visitor's language in their browser, which the server never learns, so
+ * the emails take the instance's. Any value but `"fr"` means `"en"`.
+ */
+export const EMAIL_LOCALE: EmailLocale =
+  Deno.env.get("GERBEUR_EMAIL_LOCALE")?.trim() === "fr" ? "fr" : "en";
+/**
+ * The instance's style (`GERBEUR_DEFAULT_STYLE`). The emails that aren't a
+ * user's own (the welcome and the password reset) are drawn in it. A value
+ * that isn't a style means "smooth".
+ */
+export const DEFAULT_STYLE: StyleName = (() => {
+  const style = Deno.env.get("GERBEUR_DEFAULT_STYLE")?.trim();
+  return isStyleName(style) ? style : "smooth";
+})();
 /**
  * The key lib/jwt.ts signs and verifies tokens with (`GERBEUR_JWT_SECRET`).
  * The server refuses to start without it.