feat: Implement 4 contrib-wave issues (#779 #761 #793 #780)

[ritik4ever]

• Add comparison view with side-by-side diff of two analyses
• Extend arithmetic rule S003 to detect division and modulo by zero
• Implement hosted REST API with rate limiting and auth
• Complete browser extension popup for read-only finding viewer

Closes #779

Closes #761

Closes #793

Closes #780

Summary

Describe the change, the motivation behind it, and any important implementation details.

Fixes #

Type of change

• Bug fix
• New feature
• Breaking change
• Documentation update
• Maintenance or refactor

Testing

List the commands you ran and the scope of validation.

cargo fmt --all --check
cargo clippy --workspace --all-targets --all-features -- -D warnings
cargo test -p sanctifier-core --all-features
cargo test -p sanctifier-cli
cd frontend && npm test

Checklist

• I ran the relevant tests locally, or explained why they were not needed.
• I updated documentation for any user-facing behavior changes.
• I added or updated tests for the change when appropriate.
• I added a changelog or release-notes entry when needed, or confirmed none is required.
• I verified this branch is up to date with main and merge conflicts are resolved.

[vercel]

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[drips-wave]

@ritik4ever Great news! 🎉 Based on an automated assessment of this PR, the linked Wave issue(s) no longer count against your application limits.

You can now already apply to more issues while waiting for a review of this PR. Keep up the great work! 🚀

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