build(deps): update CLI framework and security dependencies

[sameerforge]

What this PR does / why we need it:

This PR updates several core dependencies to align with modern Go patterns and address security patches. It also consolidates the internal reference for carvel.dev/kapp-controller to the stable v0.59.8 release tag.

Dependency Changes:

github.com/spf13/cobra (v1.9.1 → v1.10.2): Modernizes CLI context handling and removes deprecated YAML dependencies.

github.com/spf13/pflag (v1.0.6 → v1.0.10): Standard library patch for improved flag parsing safety.

golang.org/x/crypto (v0.45.0 → v0.50.0): Security-mandated update for cryptographic primitives.

carvel.dev/kapp-controller: Aligned internal module references to stable release v0.59.8.

Validation Results

The following verification steps were performed to ensure no regressions in CLI logic or controller reconciliation:

1. Compilation & Static Analysis

Verified that the project compiles under Go 1.25.7 and that cobra context signatures are correctly implemented.

Controller: go build -v ./cmd/controller/...

CLI: go build -v -o kctrl ./cmd/kctrl/...

2. Unit & Functional Testing

All package-level tests were executed to validate core logic, specifically around credential handling and CLI command execution.

Command: go test -v ./pkg/...

Result: All tests passed (including Helm schema generation and kctrl release runners).

3. CLI Integration & Signal Handling

Verified the functional integrity of the kctrl binary with the updated cobra and pflag versions.

Command: ./kctrl package deploy --help

Result: Verified correct flag rendering and help-text generation.

4. Dependency Integrity

Validated the state of the vendor/ directory and module checksums.

Command: go mod verify

Result: All modules verified; hashes match go.sum.

Checklist
[x] Verified builds and tests pass locally.

[x] Updated vendor/ directory via go mod vendor.

[x] Followed Carvel Contributor Guide.