Fix ImportError: add missing matplotlib dependency

Fix AttributeError: remove conflict 'from datetime import datetime'

Fix NameError: restore missing imports (io, Path)

Fix Python 3.9 type hint compatibility (remove | None syntax)

Major update: UI refactor, Real Price features, Import/Export, SPV removal (Clean Commit)

Update src/app.py

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Update src/database.py

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Update src/app.py

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Delete kaiu.ttf

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Update requirements.txt

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Update README.md

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