Add SwiftLint CI enforcement

[austin-smith]

What Changed

• Added a project SwiftLint configuration covering the app, unit tests, and UI tests.
• Added a checksum-verified SwiftLint 0.65.0 CI job that gates the macOS test and iOS build jobs.
• Configured the 800-line warning and 1,000-line error thresholds, curated safety-focused opt-in rules, and two temporary file_length exceptions.
• Refactored existing violations in place so strict lint completes cleanly without a baseline or broad source exclusions.

Why

Automated linting provides consistent code-quality enforcement in CI without coupling local Xcode builds to a developer tool installation.

The remaining oversized-file cleanup is tracked in #36.

Validation

• SwiftLint 0.65.0 strict lint: 0 violations across 75 files
• macOS build passed
• iOS Simulator build passed
• macOS test suite: 87 passed, 2 skipped, 0 failed

[chatgpt-codex-connector]

💡 Codex Review

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Reviewed commit: b8467adfdb

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[austin-smith]

@codex review

[chatgpt-codex-connector]

Codex Review: Didn't find any major issues. Keep them coming!

Reviewed commit: 9d6f2b1713

ℹ️ About Codex in GitHub

Your team has set up Codex to review pull requests in this repo. Reviews are triggered when you

• Open a pull request for review
• Mark a draft as ready
• Comment "@codex review".

If Codex has suggestions, it will comment; otherwise it will react with 👍.

Codex can also answer questions or update the PR. Try commenting "@codex address that feedback".