Refactor handleRecovery method and improve tests

- Split handleRecovery into focused helper methods for better maintainability:
  * shouldStartRecovery: handles recovery cancellation logic
  * createRecoveryContext: manages recovery context and cleanup
  * prepareForRecovery: removes DNS settings and initializes OS resolver
  * completeRecovery: resets upstream state and reapplies DNS settings
  * reinitializeOSResolver: reinitializes OS resolver with proper logging
  * Update handleRecovery documentation to reflect new orchestration role

- Improve tests:
  * Add newTestProg helper to reduce test setup duplication
  * Write comprehensive table-driven tests for all recovery methods

This refactoring improves code maintainability, testability, and reduces
complexity while maintaining the same recovery behavior. Each method now
has a single responsibility and can be tested independently.

go.mod

@@ -32,7 +32,6 @@ require (
 	github.com/quic-go/quic-go v0.48.2
 	github.com/rs/zerolog v1.28.0
 	github.com/spf13/cobra v1.8.1
-	github.com/spf13/pflag v1.0.5
 	github.com/spf13/viper v1.16.0
 	github.com/stretchr/testify v1.9.0
 	github.com/vishvananda/netlink v1.2.1-beta.2
@@ -86,6 +85,7 @@ require (
 	github.com/spf13/afero v1.9.5 // indirect
 	github.com/spf13/cast v1.6.0 // indirect
 	github.com/spf13/jwalterweatherman v1.1.0 // indirect
+	github.com/spf13/pflag v1.0.5 // indirect
 	github.com/subosito/gotenv v1.4.2 // indirect
 	github.com/u-root/uio v0.0.0-20240118234441-a3c409a6018e // indirect
 	github.com/vishvananda/netns v0.0.4 // indirect