fix(i2c): prevent file descriptor leak in SMBus usage

Fix a file descriptor leak in check_for_i2c_device.

SMBus instances were opened without being closed, causing file
descriptors to accumulate over time. In long-running scenarios,
this could reach the system ulimit and trigger:

    OSError: [Errno 24] Too many open files

As a result, flight controller boards may fail to be detected
or become inaccessible.

### Changes
- Use context manager (`with SMBus(...) as bus`) to ensure proper cleanup

### Impact
- Prevents FD exhaustion
- Improves reliability of board detection

Author: gaojulong

core/services/ardupilot_manager/flight_controller_detector/linux/linux_boards.py

@@ -23,8 +23,8 @@ def get_serials(self) -> List[Serial]:
 
     def check_for_i2c_device(self, bus_number: int, address: int) -> bool:
         try:
-            bus = SMBus(bus_number)
-            bus.read_byte_data(address, 0)
+            with SMBus(bus_number) as bus:
+                bus.read_byte_data(address, 0)
             return True
         except OSError:
             return False