fix: remove try-catch blocks that swallow exceptions

[codebutler]

Summary

• En1545 parsers (FixedInteger, FixedHex, Bitmap, Repeat, FixedString): Replace try-catch around bitParser with bounds checking (off + len <= b.size * 8). Root cause was ArrayIndexOutOfBoundsException on truncated card data.
• Oyster (Transaction, Refill, TravelPass): Replace try-catch with block bounds checking (block < sector.blocks.size). Root cause was potential IndexOutOfBoundsException on partially-read cards.
• SmartRiderTagRecord: Remove dead try-catch around readASCII() — after isASCII() returns true, readASCII() cannot throw.
• App.kt: Remove try-catch around sample import so errors bubble up to the user instead of being silently swallowed.
• ByteUtils.getHexString: Remove dead try-catch — getHexString(b) only iterates bytes and appends hex chars, it cannot throw.

Test plan

• CI tests pass (allTests)
• En1545-based transit cards (Calypso/Intercode, Mobib, etc.) still parse correctly with truncated data
• Oyster card parsing handles partially-read sectors gracefully
• SmartRider route names display correctly for both ASCII and hex data
• Sample card import shows errors to the user when import fails

🤖 Generated with Claude Code