Add optional reasons to karma voting

[konard]

Summary

Implements optional reasons for karma voting as requested in issue #117.

• ✅ Added support for optional reasons after karma operators (e.g., + решение сработало, - вопрос недостаточно конкретный)
• ✅ Modified regex pattern to capture reasons while maintaining backward compatibility
• ✅ Updated karma change messages to display reasons when provided
• ✅ Added comprehensive tests for the new functionality

Changes Made

1. Regex Pattern Updates (patterns.py)

• Modified APPLY_KARMA pattern to capture optional reasons using (?:\s+(?P<reason>.+?))?
• Maintains full backward compatibility with existing karma voting formats

2. Commands Logic (commands.py)

• Updated apply_karma() method to extract reason from matched pattern
• Modified apply_karma_change() signature to accept optional reason parameter
• Ensured reason is passed through to message building

3. Message Building (commands_builder.py)

• Enhanced build_karma_change() to include reasons in karma change notifications
• Formats reasons as Причина: {reason} when present
• Works for both collective votes and personal karma transfers

4. Testing (tests.py)

• Updated existing test to work with new method signature
• Added comprehensive test case for karma reasons functionality

Examples

Input	Result
+ решение сработало	Collective positive vote with reason "решение сработало"
- вопрос недостаточно конкретный	Collective negative vote with reason "вопрос недостаточно конкретный"
+5 отличная помощь	Transfer 5 karma with reason "отличная помощь"
+	Standard collective positive vote (no change)

Test Plan

• Verified regex pattern matches all required formats
• Tested message building with and without reasons
• Confirmed backward compatibility with existing karma voting
• Added unit tests for new functionality

Fixes #117

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