osCommerce connector: add legacy charset and currency fixture

[sridharkalaibala]

Parent: #34

Goal

Make legacy osCommerce imports safer for international stores.

Scope

Add a fixture covering non-UTF-8 text, currency symbols, and decimal formatting from an old osCommerce export.

Acceptance criteria

• Fixture includes at least two currencies and non-English product/customer names.
• Expected mapping shows normalized UTF-8 values and safe failures.
• Parser reports rows it cannot convert instead of corrupting data silently.
• No real customer data is included.

Out of scope

• No production credentials, customer records, tax IDs, payment data, or private payloads in the repo or issue comments.
• Do not claim a live integration is supported until a maintainer accepts the matching fixture and evidence.