ActiveEffects: Add complete ActiveEffects management system

- New: modules/mournblade-cyd2-effects.js with utility methods for creating, applying, and managing effects
- New: templates/partial-active-effects.hbs for displaying actor effects
- New: templates/partial-item-effects.hbs for displaying item effects
- Update: modules/mournblade-cyd2-config.js with effect configuration (types, attribute keys, categories)
- Update: templates/actor-sheet.hbs and creature-sheet.hbs with Effects tab
- Update: templates/partial-item-nav.hbs with conditional Effects tab
- Update: templates/item-talent-sheet.hbs with Effects tab content
- Update: base-actor-sheet.mjs with effect action handlers (create, edit, delete, toggle)
- Update: base-item-sheet.mjs with effect action handlers and context
- Update: modules/mournblade-cyd2-main.js to import and expose MournbladeCYD2Effects
- Update: lang/fr.json with effect-related translations

Features:
- Support for creating permanent and temporary effects
- Support for attribute modifications (ADR, PUI, CLA, PRE, TRE, etc.)
- Support for health, soul, combat, and adversity modifications
- Support for status effects
- Support for runes (pronounced and traced) effects
- Toggle to enable/disable effects
- Duration tracking (rounds, turns, seconds, combat, scene)
- Display of all active modifications summary

Generated by Mistral Vibe.
Co-Authored-By: Mistral Vibe <vibe@mistral.ai>

templates/partial-item-nav.hbs

@@ -3,5 +3,8 @@
 <nav class="sheet-tabs tabs" data-group="primary">
   <a class="item" data-tab="description">Description</a>
   <a class="item" data-tab="details">Details</a>
+  {{#if item.effects.length}}
+  <a class="item" data-tab="effects">Effets</a>
+  {{/if}}
 </nav>
 <hr />