v0.4.0 Scannable Slot Tags

Adds support for scanning QR and NFC tags that represent spool slots on a printer (AMS or similar). Filament and slot tags can be scanned in quick succession to quickly apply the filament to the slot without the user needing to interact with the UI. The tags can be scanned in either order, and new settings control which one(s) get cleared after the pair is applied.

Slot QR codes have the format SLOT|<ids>, where <ids> is the the ids value shown in the slot's data table on the Apply page. See the updated README for more info.

Other changes:

• Several new options in Settings to control new client behavior
• Optionally require user confirmation before applying a pair of scanned tags
• Add vibration and (optional) audio feedback when a tag is scanned
• Slot ids values can be copied with a click for easy pasting into a QR code generator
• Added buttons to clear active tags to the Scan and Apply pages
• Scan page now stays active by default until a valid pair of tags is scanned (configurable)
• Added a configurable delay between processing tags