Fix hold_keys dropping duplicate keys in + syntax (#1347)

[arturomaciaas]

Fixes #1347

Problem
When using the + syntax with repeated keys (e.g., KEY_4+KEY_3+KEY_5+KEY_5+KEY_9), duplicate keys were silently dropped because pressing an already-held key is a no-op at the kernel level.

Solution
The fix releases a key before re-pressing it when a duplicate is encountered in hold_keys, so that sequences like KEY_5+KEY_5 properly output both keystrokes.

What was changed

• inputremapper/injection/macros/tasks/hold_keys.py — track held codes and release before re-pressing duplicates; release each unique code once on trigger release
• tests/unit/test_macros/test_hold_keys.py — added tests for duplicate keys in both hold_keys() and + syntax

Before: KEY_4+KEY_3+KEY_5+KEY_5+KEY_9+KEY_4+KEY_1+KEY_2+KEY_8+KEY_5 = 4359128
After: KEY_4+KEY_3+KEY_5+KEY_5+KEY_9+KEY_4+KEY_1+KEY_2+KEY_8+KEY_5 = 4355941285