fix: screenshot thread safety - use fresh mss context per capture

- Remove persistent mss.mss() instance from AutoScreenshot
- Use context manager 'with mss.mss() as sct:' for each capture
- Fixes '_thread._local' object has no attribute 'srcdc' error
- Allows screenshots to work from hotkey callbacks in background threads

modules/auto_screenshot.py

@@ -24,7 +24,6 @@ class AutoScreenshot:
         self.screenshot_dir = screenshot_dir or Path.home() / ".lemontropia" / "screenshots"
         self.screenshot_dir.mkdir(parents=True, exist_ok=True)
         
-        self.capture = mss.mss()
         self.session_screenshots: List[Path] = []
         
         # Settings
@@ -41,8 +40,10 @@ class AutoScreenshot:
         filepath = self.screenshot_dir / filename
         
         try:
-            monitor = self.capture.monitors[1]  # Primary monitor
-            screenshot = self.capture.grab(monitor)
+            # Create fresh mss context for thread safety
+            with mss.mss() as sct:
+                monitor = sct.monitors[1]  # Primary monitor
+                screenshot = sct.grab(monitor)
                 img = np.array(screenshot)
                 img = cv2.cvtColor(img, cv2.COLOR_BGRA2BGR)
                 cv2.imwrite(str(filepath), img)
@@ -63,8 +64,10 @@ class AutoScreenshot:
         filepath = self.screenshot_dir / filename
         
         try:
+            # Create fresh mss context for thread safety
+            with mss.mss() as sct:
                 monitor = {"left": x, "top": y, "width": w, "height": h}
-            screenshot = self.capture.grab(monitor)
+                screenshot = sct.grab(monitor)
                 img = np.array(screenshot)
                 img = cv2.cvtColor(img, cv2.COLOR_BGRA2BGR)
                 cv2.imwrite(str(filepath), img)