Replace pandas with stdlib csv, apprise with direct Slack webhook, switch to opencv-headless

- Rewrite csv_exporter.py to use stdlib csv.DictWriter instead of pandas DataFrame
- Rewrite notifications.py to use aiohttp direct Slack webhook instead of apprise
- Switch opencv-python to opencv-python-headless in pyproject.toml
- Move httpx from dev to prod dependencies
- Remove pandas and apprise from mypy ignore_missing_imports

notifications.py

@@ -1,29 +1,27 @@
-from abc import abstractmethod
-import apprise
-from functools import lru_cache
+import json
+import logging
 import os
 
+import aiohttp
 
-class Surface:
-    @abstractmethod
-    def connection_string(self) -> str | None: ...
-
-
-class Slack(Surface):
-    def connection_string(self) -> str | None:
-        return os.environ.get("SLACK_WEBHOOK_URL")
-
-
-@lru_cache(maxsize=None)
-def get_notifier() -> apprise.Apprise:
-    surfaces = [Slack()]
-    obj = apprise.Apprise()
-    for surface in surfaces:
-        if conn := surface.connection_string():
-            obj.add(conn)
-    return obj
+logger = logging.getLogger(__name__)
 
 
 async def send_notification(body: str, title: str = "") -> bool:
-    notifier = get_notifier()
-    return await notifier.async_notify(body=body, title=title)
+    webhook_url = os.environ.get("SLACK_WEBHOOK_URL")
+    if not webhook_url:
+        logger.debug("No SLACK_WEBHOOK_URL configured, skipping notification")
+        return False
+
+    text = f"*{title}*\n{body}" if title else body
+    try:
+        async with aiohttp.ClientSession() as session:
+            async with session.post(
+                webhook_url,
+                data=json.dumps({"text": text}),
+                headers={"Content-Type": "application/json"},
+            ) as resp:
+                return resp.status == 200
+    except Exception:
+        logger.exception("Failed to send Slack notification")
+        return False