Fix SpoolBuddy daemon failing to import hardware drivers

The daemon imports read_tag and scale_diag as bare modules, but they
live in spoolbuddy/scripts/ which isn't on sys.path when systemd runs
the daemon. Added scripts/ to sys.path at startup, resolved relative
to the module file. Also moved the read_tag import inside NFCReader's
try/except (was crashing the daemon instead of skipping gracefully)
and demoted hardware-not-available messages from ERROR to INFO.

spoolbuddy/daemon/scale_reader.py

@@ -27,7 +27,7 @@ class ScaleReader:
             self._ok = True
             logger.info("Scale initialized (tare=%d, cal=%.6f)", tare_offset, calibration_factor)
         except Exception as e:
-            logger.error("Scale init failed: %s", e)
+            logger.info("Scale not available: %s", e)
 
     @property
     def ok(self) -> bool: