Fix SpoolBuddy daemon crash when read_tag module is missing

NFCReader.__init__ imported read_tag and instantiated PN5180() outside
the try/except block, so a missing module crashed the entire daemon.
Moved the import inside the existing try/except so the daemon gracefully
skips NFC polling — matching the scale reader's existing behavior.

CHANGELOG.md

@@ -8,6 +8,9 @@ All notable changes to Bambuddy will be documented in this file.
 - **SpoolBuddy AMS Page: External Slots & Slot Configuration** — The SpoolBuddy AMS page (`/spoolbuddy/ams`) now displays external spool slots (single nozzle: "Ext", dual nozzle: "Ext-L"/"Ext-R") and AMS-HT units in a compact horizontal row below the regular AMS grid, fitting within the 1024×600 kiosk display without scrolling. Clicking any AMS, AMS-HT, or external slot opens the `ConfigureAmsSlotModal` to configure filament type and color — the same modal used on the main Printers page. Dual-nozzle printers show L/R nozzle badges on each AMS unit. Temperature and humidity are displayed with threshold-colored SVG icons (green/gold/red) matching the Bambu Lab style on the main printer cards, using the configured AMS humidity and temperature thresholds from settings.
 - **SpoolBuddy Dashboard Redesign** — Redesigned the SpoolBuddy dashboard with a two-column layout: left column shows device connection status (scale and NFC with state-colored icons — green when device is online, gray when offline) and a compact printers list with live status indicators; right column shows the current spool card. Cards use a dashed border style for a cleaner look. The large weight display card was removed in favor of the inline scale reading in the device card.
 
+### Fixed
+- **SpoolBuddy Daemon Crashes When NFC Module Not Installed** — The `NFCReader` constructor imported `read_tag` and instantiated `PN5180()` outside the try/except block, so a missing `read_tag` module raised an uncaught `ModuleNotFoundError` that crashed the entire daemon via `asyncio.gather`. The scale reader already handled its missing module gracefully. Moved the import and instantiation inside the existing try/except so a missing NFC driver sets `ok=False` and the daemon logs "NFC reader not available" and continues running the scale and heartbeat loops.
+
 ### Improved
 - **SpoolBuddy Scale Value Stabilization** — The SpoolBuddy daemon now suppresses redundant scale weight reports: only sends updates when the weight changes by ≥2g or the stability state flips (stable ↔ unstable). Previously every 1-second report interval sent a reading regardless of change, causing the dashboard weight display to bounce continuously. The frontend also applies a 3g display threshold as defense-in-depth.
 - **SpoolBuddy TopBar: Online Printer Selection** — The printer selector in the SpoolBuddy top bar now only shows online printers and auto-selects the first online printer. If the currently selected printer goes offline, it automatically switches to the next available online printer. Also replaced the placeholder icon with the SpoolBuddy logo.

spoolbuddy/daemon/nfc_reader.py

@@ -16,9 +16,7 @@ class NFCState(Enum):
 
 class NFCReader:
     def __init__(self):
-        from read_tag import PN5180
-
-        self._nfc = PN5180()
+        self._nfc = None
         self._state = NFCState.IDLE
         self._current_uid: str | None = None
         self._current_sak: int | None = None
@@ -26,6 +24,9 @@ class NFCReader:
         self._ok = False
 
         try:
+            from read_tag import PN5180
+
+            self._nfc = PN5180()
             self._nfc.reset()
             self._nfc.load_rf_config(0x00, 0x80)
             time.sleep(0.010)
@@ -35,7 +36,7 @@ class NFCReader:
             self._ok = True
             logger.info("NFC reader initialized")
         except Exception as e:
-            logger.error("NFC reader init failed: %s", e)
+            logger.error("NFC init failed: %s", e)
 
     @property
     def ok(self) -> bool: