fix: read profile manifests as utf-8 on Windows

[kodroi]

Summary

Windows profile reads now treat Stream Deck profile and page manifests as UTF-8, which stops streamdeck_read_profiles from crashing when a manifest contains emoji or other non-ASCII text.

The change keeps encoding decisions in the existing JSON helper layer by making manifest reads and atomic writes explicit about UTF-8 instead of inheriting the process codepage.

The regression test writes a real UTF-8 page manifest with "pastedText": "👍" and verifies both list_profiles() and read_page() can load it.

Closes #39.

Testing

• uv run pytest tests\\test_profile_manager.py -k utf8 -q
• uv run ruff check tests\\test_profile_manager.py profile_manager.py

[Copilot]

Pull request overview

Fixes Windows crashes when reading Stream Deck profile/page manifests containing non-ASCII (e.g., emoji) by forcing JSON reads/writes to use UTF-8 in the shared helper layer, and adds a regression test covering UTF-8 emoji content in a page manifest.

Changes:

• Read JSON manifests with Path.read_text(encoding="utf-8") in the JSON loader.
• Write JSON manifests atomically with Path.write_text(..., encoding="utf-8").
• Add a regression test that writes a UTF-8 page manifest containing "pastedText": "👍" and verifies list_profiles() + read_page() can load it.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
tests/test_profile_manager.py	Ensures test fixtures and new regression test write UTF-8 JSON and validates emoji survives a full load path.
profile_manager.py	Makes JSON load/atomic write explicitly UTF-8 to avoid Windows codepage-dependent decoding/encoding.

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[jack-arturo]

@copilot apply changes based on the comments in this thread