Refactor OnComboCompleteListener: split handler and make feedback configurable/localized

[DiamondDagger590]

Context

us.eunoians.mcrpg.listener.ability.OnComboCompleteListener#onComboComplete is a ~90-line @EventHandler that inlines every precondition check, feedback message, sound cue, and ability dispatch into a single method. A TODO(backlog) immediately above the method references this ticket.

Problems

Structural:

• One method does ability resolution, world-enablement gating, cooldown checking, mana checking, feedback messaging, ability dispatch, and cooldown application.
• Hard to add a new precondition (e.g., stamina, debuff gating) without making the method longer.
• Hard to test — each branch requires a full Bukkit event setup.

Hard-coded values:

• Feedback strings: "On Cooldown (Ns)", "Not Enough Mana", "X is on cooldown!", "Not enough mana to use X!".
• Sounds: Sound.UI_BUTTON_CLICK (no ability at slot), Sound.BLOCK_NOTE_BLOCK_BASS (cooldown / insufficient mana) with hard-coded pitch/volume.
• CENTER_CONTENT_DURATION_TICKS = 60L — how long the action-bar feedback persists.
• All strings bypass the localization system entirely.

Proposed work

Structural:

• Split the handler into per-precondition private helpers (or a small ComboActivationDispatcher collaborator) that each return a result type indicating success, skip, or failure-with-feedback.
• Leave the @EventHandler method short — resolve the ability and delegate.

Configuration:

• Move feedback sounds, volumes, pitches, and the center-content persistence duration into combo.yml with Route constants on ComboConfigFile.
• Route all player-facing strings (action bar + chat) through McRPGLocalizationManager with new LocalizationKey routes and entries in every bundled locale YAML (English minimum).

Acceptance criteria

• onComboComplete is at most ~20 lines; preconditions are extracted into named helpers or a collaborator.
• No user-facing strings live in the listener — all routed through LocalizationKey + McRPGLocalizationManager.
• Sounds, volumes, pitches, and feedback duration come from combo.yml.
• Unit tests cover the precondition helpers (or collaborator) without needing a live event.
• TODO(backlog) above the method is removed.