Update admin theme/layout and refresh README details.

Align the project baseline with the latest admin interface styling and layout structure while documenting setup and usage updates in README.

apps/api/app/core/email.py

@@ -0,0 +1,61 @@
+from __future__ import annotations
+
+import smtplib
+from dataclasses import dataclass
+from email.message import EmailMessage
+
+from app.core.config import settings
+
+
+@dataclass
+class SentEmail:
+    to: str
+    subject: str
+    body: str
+    template: str
+
+
+class MemoryMailer:
+    def __init__(self) -> None:
+        self.sent: list[SentEmail] = []
+
+    def send(self, to: str, subject: str, body: str, template: str) -> None:
+        self.sent.append(SentEmail(to=to, subject=subject, body=body, template=template))
+
+    def clear(self) -> None:
+        self.sent.clear()
+
+    def latest_token(self, recipient: str, template: str) -> str | None:
+        for message in reversed(self.sent):
+            if message.to == recipient and message.template == template:
+                for line in message.body.splitlines():
+                    if line.startswith("TOKEN:"):
+                        return line.split(":", 1)[1].strip()
+        return None
+
+
+class SmtpMailer:
+    def send(self, to: str, subject: str, body: str, template: str) -> None:
+        _ = template
+        message = EmailMessage()
+        message["From"] = settings.smtp_from
+        message["To"] = to
+        message["Subject"] = subject
+        message.set_content(body)
+        with smtplib.SMTP(settings.smtp_host, settings.smtp_port, timeout=10) as smtp:
+            if settings.smtp_user:
+                smtp.login(settings.smtp_user, settings.smtp_password)
+            smtp.send_message(message)
+
+
+memory_mailer = MemoryMailer()
+
+
+def get_mailer():
+    if settings.email_delivery_mode == "memory":
+        return memory_mailer
+    return SmtpMailer()
+
+
+def send_template_email(to: str, template: str, subject: str, body: str) -> None:
+    get_mailer().send(to=to, subject=subject, body=body, template=template)