feat(import-wizard): add step 4 for import preview and enhance step 3… (#11)

* feat(import-wizard): add step 4 for import preview and enhance step 3 with column mapping functionality

* Realign import wizard steps 2 & 3 with design spec (#12)

* Initial plan

* feat(import-wizard): align Step 2 and Step 3 with design spec

- Step 2: Added column mapping dropdowns with manual override
- Step 2: Added duplicate mapping warning
- Step 3: Changed from column mapping to parsing configuration
- Step 3: Added date format presets, decimal/thousands separators, rows to skip, save template options

Co-authored-by: PhantomDave <34485699+PhantomDave@users.noreply.github.com>

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Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: PhantomDave <34485699+PhantomDave@users.noreply.github.com>

* Fix code review issues in import wizard step 4 preview (#13)

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Co-authored-by: Copilot <198982749+Copilot@users.noreply.github.com>

Author: PhantomDave