ft: Replace gorilla gorilla/mux with chi router

[descholar-ceo]

What does this PR do?

Type of change

• Bug fix
• New command or flag
• Skeleton template change (affects gofasta new output)
• Generation template change (affects gofasta g output)
• Refactor / cleanup
• Documentation
• Other (describe below)

How to test

# Build the CLI
go build -o /tmp/gofasta ./cmd/gofasta/

# Create a test project
/tmp/gofasta new /tmp/testproject

# Verify it compiles
cd /tmp/testproject && go build ./...

Checklist

• go test ./... passes
• golangci-lint run passes
• If skeleton templates changed: generated project compiles with go build ./...
• If generation templates changed: tested with gofasta g scaffold
• Related issue linked (e.g. Fixes #123)

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

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