feat: add Equipment tab with slot-type validation

Add a new Equipment tab to manage player gear and stat bonuses.

Features:
- 19 equipment slots across 8 categories (helmet, necklace, body armor, gloves, pants, shoes, rings, accessories)
- Type-to-slot validation: each type has max equipped limits (1 helmet, 10 rings, 3 accessories, etc.)
- Auto-slot assignment: equipping a ring fills the first available ring slot
- Stat bonuses from equipped items display on RPG attributes (e.g. STR 10 +2)
- Create/edit modal with stat checkboxes per RPG attribute
- Inventory list for unequipped items

Architecture:
- Shared constants in src/systems/equipment/constants.js
- Category-based types (Ring, Accessory) with auto-slot assignment
- v7 migration converts legacy slot-specific types to generic categories
- Full i18n support for all UI strings

Files:
- New: src/systems/equipment/constants.js
- New: src/systems/interaction/equipmentActions.js
- New: src/systems/rendering/equipment.js
- Modified: state.js, persistence.js, template.html, index.js
- Modified: userStats.js, desktop.js, mobile.js, layout.js, modals.js
- Modified: apiClient.js, sillytavern.js, style.css, en.json

src/systems/generation/apiClient.js

@@ -32,6 +32,7 @@ import { renderInfoBox } from '../rendering/infoBox.js';
 import { removeLocks } from './lockManager.js';
 import { renderThoughts } from '../rendering/thoughts.js';
 import { renderInventory } from '../rendering/inventory.js';
+import { renderEquipment } from '../rendering/equipment.js';
 import { renderQuests } from '../rendering/quests.js';
 import { renderMusicPlayer } from '../rendering/musicPlayer.js';
 import { i18n } from '../../core/i18n.js';
@@ -356,6 +357,7 @@ export async function updateRPGData(renderUserStats, renderInfoBox, renderThough
             renderInfoBox();
             renderThoughts();
             renderInventory();
+            renderEquipment();
             renderQuests();
             renderMusicPlayer($musicPlayerContainer[0]);