Parses a Taiwanese address into structured fields and returns a canonical form. Handles the things that break naive parsers: 台/臺 spelling, full-width digits, Chinese numerals (三十五巷 -> lane 35), pre-merger county names (臺北縣 -> 新北市), 之/- door numbers, and 段巷弄 nesting. Returns whatever it could not place in `unparsed`, so partial results are visible rather than silently wrong.