fix: allow hex input in UintSlice

[happysnaker]

Summary

• make UintSlice parse values with base autodetection instead of decimal-only parsing
• keep UintSlice aligned with other integer slice flags that already accept 0x input
• add regression coverage for hexadecimal UintSlice values

Problem

Issue #229 reports that UintSliceVar rejects inputs like 0x86 even though other integer slice flags accept Go-style base prefixes. Today UintSlice uses strconv.ParseUint(..., 10, 0) in parsing, replacement, and getter conversion paths, so hexadecimal values fail unexpectedly.

Fix

Switch the UintSlice parsing paths to strconv.ParseUint(..., 0, 0) so base prefixes are handled consistently across parse, replace, and GetUintSlice().

Closes #229

[happysnaker]

Maintainer context: this is intended as a minimal consistency fix for UintSlice, not a new flag syntax. strconv.ParseUint(..., 0, 0) already matches Go's normal integer literal behavior (123, 077, 0x86), so this just brings the slice variant in line with that expectation and with the linked report in #229.

[tomasaschan]

Changes look OK to me, but there are some stray things around IP address parsing that have snuck into the diff. Needs a rebase, maybe?

[happysnaker]

Rebased and force-pushed on July 2, 2026 to drop the unrelated ip.go / ip_test.go hunks that had accidentally slipped into the branch. The PR is back to the minimal UintSlice-only diff now (298bcdf). CI should rerun from the cleaned branch.

[tomasaschan]

Thanks for these contributions!