Import Feather CSV transaction descriptions

[louiss72]

Fixes #1014.

Summary:

• add a Feather CSV transaction-note parser for the documented txid and description columns
• add a wallet menu action to pick a Feather CSV via Android's document picker
• import non-empty descriptions with Wallet.setUserNote, preserving existing Monerujo/xmr.to note metadata where present
• add unit coverage for quoted descriptions, commas, escaped quotes, missing values, missing columns, and empty files

Verification:

• git diff --check
• Not run: ./gradlew testProdMainnetDebugUnitTest --tests com.m2049r.xmrwallet.util.FeatherCsvTxNotesTest because this local environment has no Java Runtime installed.

Bounty payout address (XMR):
4DSQMNzzq46N1z2pZWAVdeA6JvUL9TCB2bnBiA3ZzoqEdYJnMydt5akCa3vtmapeDsbVKGPFdNkzqTcJS8M8oyK7WGjNk99k1B6CoKjvH5