ux: standardize --name vs --key-name flag across commands

## Description

Key commands use `--name` for the key identifier, but the global flag is `--key-name`. This inconsistency is confusing for users.

## Current behavior

- `platform keys import --name mykey` (local flag)
- `platform wallet balance --key-name mykey` (global flag)

Two different flag names for the same concept.

## Expected behavior

Standardize on `--key-name` everywhere, or alias `--name` to `--key-name` in key commands.

## Files affected
- `cmd/keys.go` (lines 464, 468, 475, 479, 483) - uses `--name`
- `cmd/root.go` (line 65) - uses `--key-name`

## Severity
High UX impact - confusing for new users

## Source
CLI UX audit (2026-02-09)

Start in cmd/keys.go at lines 464, 468, 475, 479, and 483, then compare those flags with --key-name in cmd/root.go at line 65. Decide whether the commands should use the standardized flag or provide an alias, based on the issue's expected behavior. Done means the key-related commands no longer present inconsistent names.

Written by the indexing model from the issue text.