feat(scanner): resolve cross-file constants and imported axios instances

[felmonon]

Summary

Handlers and calls built from cross-file constants or imported axios.create(...) instances are currently reported as unsupported (see README limitations). These are common in real projects and inflate the unsupported count.

Scope

• Resolve string/URL constants imported from other files
• Resolve axios instances created in one file and imported into another

Acceptance criteria

• A cross-file const BASE = '...' used in a handler/call resolves to a concrete pattern
• Imported axios instance calls are detected like same-file instances
• New fixtures cover both cases
• Patterns that genuinely cannot be resolved still fall back to unsupported (no guessing)

Why

Reducing false "unsupported" results directly improves the tool's accuracy and trust.