v0.2.0: Barcode food logging

Everything since v0.1.0. Details in CHANGELOG.md.

New

• Barcode scanning: point the camera at a packaged food and log the meal from the label
• Open Food Facts lookup for unknown barcodes: server-side, carries the barcode and nothing else, off switch in Settings and a veto in config
• A second scan of the same product resolves from your own presets with no network request
• "Unspent this month" on the Money tab: logged income minus logged spend and set-asides
• A speech model picker in Settings that offers only models on the server's disk and never downloads
• The licence and a source link in Settings (AGPL section 13)
• The attach question shows your saved figure and date beside the scanned label's

Fixed

• The scan sheet could be covered by the phone's tab bar; it now draws above everything
• Changing the speech model on a running server was silently ignored until a restart
• A speech model name written through the API could trigger a download; models not on disk are refused
• The Settings page could name two different speech models at once
• Preset rows crushed their name when the delete confirmation appeared

Changed

• The scan sheet is redesigned: found products render as a card with an energy and serving row, a viewfinder that names which barcode reader is running, and every failure states itself in a sentence
• Empty states space their action buttons apart