feat: proactive notifications — email, NC Talk, Google Chat per user

notification.py now handles all three outbound channels. Email defaults
to the user's login address (google_email from auth.json); an optional
override can be set in channels.json. Google Chat uses an incoming
webhook URL. NC Talk was already wired, just needs notification_room set.

Settings page gains a Notifications section: channel dropdown, optional
email override, NC room token, and Google Chat webhook URL. All stored
in per-user channels.json.

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

cortex/routers/settings.py

@@ -18,7 +18,7 @@ import jwt
 from fastapi import APIRouter, Form, Request
 from fastapi.responses import HTMLResponse, RedirectResponse
 
-from auth_utils import COOKIE_NAME, decode_token, check_credentials, set_password, _read_auth, _write_auth
+from auth_utils import COOKIE_NAME, decode_token, check_credentials, set_password, _read_auth, _write_auth, get_user_channels
 from persona import list_user_personas
 from config import settings as app_settings
 
@@ -73,6 +73,17 @@ def _settings_page(username: str, personas: list[str], back_persona: str = "", s
         allowlist_text = ""
     html = html.replace("{{ email_allowlist }}", allowlist_text)
 
+    # Notification channel settings
+    channels     = get_user_channels(username)
+    notify_ch    = _html.escape(channels.get("notification_channel", "") or "")
+    notify_email = _html.escape(channels.get("notification_email", "") or "")
+    nc_room      = _html.escape((channels.get("nextcloud") or {}).get("notification_room", "") or "")
+    gc_webhook   = _html.escape((channels.get("google_chat") or {}).get("outbound_webhook", "") or "")
+    html = html.replace("{{ notify_channel }}", notify_ch)
+    html = html.replace("{{ notify_email_override }}", notify_email)
+    html = html.replace("{{ nc_notify_room }}", nc_room)
+    html = html.replace("{{ gc_webhook }}", gc_webhook)
+
     persona_items = "\n".join(
         f'''<li>
           <a href="/{username}/{p}" class="persona-link">{p}</a>
@@ -240,6 +251,57 @@ async def rename_persona(
     return RedirectResponse("/settings", status_code=302)
 
 
+@router.post("/settings/notifications", include_in_schema=False)
+async def save_notifications(
+    request: Request,
+    notification_channel: str = Form(""),
+    notification_email: str = Form(""),
+    nc_notification_room: str = Form(""),
+    gc_outbound_webhook: str = Form(""),
+):
+    username = _get_session_user(request)
+    if not username:
+        return RedirectResponse("/login", status_code=302)
+
+    personas     = list_user_personas(username)
+    back_persona = _preferred_persona(request, username)
+
+    channels_path = app_settings.home_root() / username / "channels.json"
+    try:
+        channels = json.loads(channels_path.read_text())
+    except Exception:
+        channels = {}
+
+    # Top-level notification preference
+    notification_channel = notification_channel.strip()
+    if notification_channel in ("email", "nextcloud", "google_chat"):
+        channels["notification_channel"] = notification_channel
+    else:
+        channels.pop("notification_channel", None)
+
+    # Optional email address override (blank = use login email)
+    notification_email = notification_email.strip()
+    if notification_email:
+        channels["notification_email"] = notification_email
+    else:
+        channels.pop("notification_email", None)
+
+    # NC Talk notification room — nested under "nextcloud"
+    if "nextcloud" not in channels:
+        channels["nextcloud"] = {}
+    channels["nextcloud"]["notification_room"] = nc_notification_room.strip()
+
+    # Google Chat outbound webhook — nested under "google_chat"
+    if "google_chat" not in channels:
+        channels["google_chat"] = {}
+    channels["google_chat"]["outbound_webhook"] = gc_outbound_webhook.strip()
+
+    channels_path.write_text(json.dumps(channels, indent=2) + "\n")
+    logger.info("notifications updated for %s (channel=%s)", username, notification_channel or "none")
+    return HTMLResponse(_settings_page(username, personas, back_persona,
+                                       success="Notification settings saved."))
+
+
 @router.post("/settings/email-allowlist", include_in_schema=False)
 async def save_email_allowlist(
     request: Request,