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/notification.py

@@ -1,22 +1,21 @@
 """
 Outbound notification helpers — send messages to user channels proactively.
 
-Channel config lives in home/{user}/channels.json.
-Each channel that supports proactive notifications needs a notification_channel
-set to its key name (e.g. "nextcloud", "google_chat") in the user's channels.json:
+Channel config lives in home/{user}/channels.json:
   {
-    "notification_channel": "nextcloud",
+    "notification_channel": "email" | "nextcloud" | "google_chat",
+    "notification_email":   "<override address — defaults to login email>",
     "nextcloud": {
-      "url": "https://cloud.example.com",
-      "bot_secret": "...",
-      "notification_room": "<room-token>",
-      ...
+      "url": "...", "bot_secret": "...", "notification_room": "<token>", ...
+    },
+    "google_chat": {
+      "outbound_webhook": "https://chat.googleapis.com/v1/spaces/...", ...
     }
   }
 
 If notification_channel is absent, defaults to "nextcloud" if configured.
-If notification_room (for NCT) is absent, notifications are silently skipped.
 """
+import asyncio
 import hashlib
 import hmac
 import json
@@ -73,34 +72,89 @@ async def _notify_nct(nct: dict, message: str, username: str) -> None:
     await _send_nct_message(url, secret, room, message)
 
 
+async def _notify_email(username: str, message: str, email_override: str | None = None) -> None:
+    """Send notification via email. Address = override → google_email from auth.json."""
+    from auth_utils import _read_auth
+    from email_utils import send_email
+
+    to_addr = email_override or _read_auth(username).get("google_email", "").strip()
+    if not to_addr:
+        logger.warning("notify: no email address for %s — set notification_email in channels.json", username)
+        return
+
+    ok = await asyncio.to_thread(
+        send_email,
+        to_email=to_addr,
+        subject="Cortex",
+        body_text=message,
+        body_html=message.replace("\n", "<br>"),
+    )
+    if ok:
+        logger.info("notify email → %s (%d chars)", to_addr, len(message))
+    else:
+        logger.warning("notify: email send failed for %s", username)
+
+
+async def _notify_google_chat(webhook_url: str, message: str, username: str) -> None:
+    """POST a message to a Google Chat space via incoming webhook."""
+    body = json.dumps({"text": message}, ensure_ascii=False).encode("utf-8")
+    try:
+        async with httpx.AsyncClient() as client:
+            resp = await client.post(
+                webhook_url,
+                content=body,
+                headers={"Content-Type": "application/json"},
+                timeout=15,
+            )
+        if resp.status_code not in (200, 201):
+            logger.warning("notify Google Chat %s → HTTP %d: %s", username, resp.status_code, resp.text[:200])
+        else:
+            logger.info("notify Google Chat → %s (%d chars)", username, len(message))
+    except Exception as e:
+        logger.error("notify Google Chat error for %s: %s", username, e)
+
+
 async def notify(username: str, message: str, channel: str | None = None) -> None:
     """Send a notification to the user's preferred outbound channel.
 
     Channel resolution order:
       1. `channel` parameter if provided
       2. `notification_channel` key in channels.json
-      3. "nextcloud" if configured
+      3. "nextcloud" if notification_room is configured
       4. Silent no-op
 
-    To configure: set `notification_channel` in home/{user}/channels.json.
-    For NCT: also set `notification_room` in the nextcloud section.
+    Configure via home/{user}/channels.json — see module docstring.
     """
     from auth_utils import get_user_channels
     channels = get_user_channels(username)
 
     target = channel or channels.get("notification_channel", "").strip()
     if not target:
-        # Auto-detect: use nextcloud if configured
-        if "nextcloud" in channels:
+        # Auto-detect: nextcloud if a notification_room is set
+        nct = channels.get("nextcloud", {})
+        if nct.get("notification_room", "").strip():
             target = "nextcloud"
         else:
             return
 
-    if target == "nextcloud":
+    if target == "email":
+        email_override = channels.get("notification_email", "").strip() or None
+        await _notify_email(username, message, email_override=email_override)
+
+    elif target == "nextcloud":
         nct = channels.get("nextcloud")
         if not nct:
             logger.debug("notify: nextcloud not configured for %s", username)
             return
         await _notify_nct(nct, message, username)
+
+    elif target == "google_chat":
+        gc = channels.get("google_chat", {})
+        webhook = gc.get("outbound_webhook", "").strip()
+        if not webhook:
+            logger.debug("notify: google_chat outbound_webhook not set for %s", username)
+            return
+        await _notify_google_chat(webhook, message, username)
+
     else:
-        logger.debug("notify: channel %r not yet supported for outbound (user %s)", target, username)
+        logger.debug("notify: channel %r not supported for outbound (user %s)", target, username)