feat: email notifications with tabbed channel UI (v0.9.10)

Add email as a second notification channel alongside ntfy:
- Tabbed channel selector: ntfy | Email | Telegram (coming soon) | Discord (coming soon)
- Active channel shown with green status dot on tab
- Email tab: address input, Save & Enable, Test, Disable — same UX pattern as ntfy
- Backend: SMTP config in settings (SMTP_HOST/PORT/USER/PASSWORD/FROM/STARTTLS)
- Dispatcher: _send_email() helper wired into dispatch_notifications
- POST /api/notifications/test/email endpoint with descriptive error messages
- Email fires in same window as ntfy (respects quiet hours / digest hold)
- Telegram and Discord tabs show coming-soon banners with planned feature description
- .env.example documents all SMTP settings with provider examples

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/app/api/notifications.py

@@ -45,6 +45,8 @@ def _prefs_to_response(prefs: dict, rss_token: str | None) -> NotificationSettin
         ntfy_enabled=prefs.get("ntfy_enabled", False),
         rss_enabled=prefs.get("rss_enabled", False),
         rss_token=rss_token,
+        email_enabled=prefs.get("email_enabled", False),
+        email_address=prefs.get("email_address", ""),
         digest_enabled=prefs.get("digest_enabled", False),
         digest_frequency=prefs.get("digest_frequency", "daily"),
         quiet_hours_start=prefs.get("quiet_hours_start"),
@@ -91,6 +93,10 @@ async def update_notification_settings(
         prefs["ntfy_enabled"] = body.ntfy_enabled
     if body.rss_enabled is not None:
         prefs["rss_enabled"] = body.rss_enabled
+    if body.email_enabled is not None:
+        prefs["email_enabled"] = body.email_enabled
+    if body.email_address is not None:
+        prefs["email_address"] = body.email_address.strip()
     if body.digest_enabled is not None:
         prefs["digest_enabled"] = body.digest_enabled
     if body.digest_frequency is not None:
@@ -175,6 +181,54 @@ async def test_ntfy(
         return NotificationTestResult(status="error", detail=f"Connection error: {e}")
 
 
+@router.post("/test/email", response_model=NotificationTestResult)
+async def test_email(
+    current_user: User = Depends(get_current_user),
+    db: AsyncSession = Depends(get_db),
+):
+    """Send a test email to the user's configured email address."""
+    import smtplib
+    from email.mime.text import MIMEText
+
+    user = await db.get(User, current_user.id)
+    prefs = user.notification_prefs or {}
+    email_addr = prefs.get("email_address", "").strip()
+    if not email_addr:
+        return NotificationTestResult(status="error", detail="No email address saved. Save your address first.")
+
+    if not app_settings.SMTP_HOST:
+        return NotificationTestResult(status="error", detail="SMTP not configured on this server. Set SMTP_HOST in .env")
+
+    try:
+        from_addr = app_settings.SMTP_FROM or app_settings.SMTP_USER
+        base_url = (app_settings.PUBLIC_URL or app_settings.LOCAL_URL).rstrip("/")
+        body = (
+            "This is a test email from PocketVeto.\n\n"
+            "Your email notification settings are working correctly. "
+            "Real alerts will include bill titles, summaries, and direct links.\n\n"
+            f"Visit your notifications page: {base_url}/notifications"
+        )
+        msg = MIMEText(body, "plain", "utf-8")
+        msg["Subject"] = "PocketVeto: Test Email Notification"
+        msg["From"] = from_addr
+        msg["To"] = email_addr
+
+        with smtplib.SMTP(app_settings.SMTP_HOST, app_settings.SMTP_PORT, timeout=10) as s:
+            if app_settings.SMTP_STARTTLS:
+                s.starttls()
+            if app_settings.SMTP_USER:
+                s.login(app_settings.SMTP_USER, app_settings.SMTP_PASSWORD)
+            s.sendmail(from_addr, [email_addr], msg.as_string())
+
+        return NotificationTestResult(status="ok", detail=f"Test email sent to {email_addr}")
+    except smtplib.SMTPAuthenticationError:
+        return NotificationTestResult(status="error", detail="SMTP authentication failed — check SMTP_USER and SMTP_PASSWORD in .env")
+    except smtplib.SMTPConnectError:
+        return NotificationTestResult(status="error", detail=f"Could not connect to {app_settings.SMTP_HOST}:{app_settings.SMTP_PORT}")
+    except Exception as e:
+        return NotificationTestResult(status="error", detail=str(e))
+
+
 @router.post("/test/rss", response_model=NotificationTestResult)
 async def test_rss(
     current_user: User = Depends(get_current_user),