Add VoteStreak migration, recurring option, and legacy progress migration

[BenCodez]

Motivation

• Provide an automated way to migrate the old VoteStreak config layout into the new VoteStreaks format and preserve existing user progress.
• Introduce a Recurring option to allow streaks to either reward every N completions or only once at N.

Description

• Added a recurring boolean to VoteStreakDefinition with constructors updated to preserve default behavior.
• Changed reward logic in VoteStreakHandler.processVoteForDefinition to differentiate recurring rewards (every N completions) from one-time rewards (only at exactly N).
• Implemented legacy progress migration so a user with old per-day/week/month streak counters will have that progress migrated into the new streak StreakState on first access.
• Added migrateLegacyConfigManually() and legacy loader VoteStreakConfigLoader.loadLegacy to convert old VoteStreak sections into VoteStreaks, including creating new definition IDs, moving rewards, and marking legacy entries disabled.
• Exposed an admin command MigrateVoteStreaks (shown as /av migratevotestreaks in logs) in CommandLoader to trigger migration and reload.
• Updated VoteStreak configuration sample SpecialRewards.yml to document the Recurring option and to include the new example field.
• Updated and expanded unit tests and small test helpers in VoteStreakHandlerTest to cover loading, legacy-state upgrade, and config migration behaviors.

Testing

• Ran the VoteStreakHandlerTest JUnit suite which includes tests for config loading, old-state upgrades, legacy-progress migration, and config migration, and all tests passed.
• Verified that the config loader warns when VoteStreaks is missing and suggests running the migration command.

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Codex Task