docs: update define imports to use @/utils.ts alias

[eaallen]

Summary

• Update outdated documentation code examples that imported define from relative paths (../utils.ts and ../../utils.ts)
• Replace them with the @/utils.ts alias to match current Fresh project conventions

Test plan

• Verified no remaining ../utils.ts or ../../utils.ts imports in docs/latest/
• Spot-check updated pages on usefresh.dev after merge (getting started, middleware, layouts, testing, advanced guides)

Made with Cursor

[eaallen]

I just noticed some of the examples use the old ../utils import method instead of @/utils. When I was first learning about fresh having to deal with the relative imports was frustrating. So I am updating the docs to make this smoother for other people.

I will also mention that some of the docs already used the @/utils, so this is just ensuring we use the same semantics throughout the docs.