refactor: extract rendering systems

Extract rendering logic from index.js into modular system:
- src/utils/avatars.js: Safe thumbnail URL generation with error handling
- src/systems/rendering/userStats.js: User stats panel with progress bars and classic RPG stats
- src/systems/rendering/infoBox.js: Info box dashboard with weather, date, time, and location widgets
- src/systems/rendering/thoughts.js: Character thoughts panel and floating chat bubbles

Reduces index.js from 3,829 to 2,430 lines (-1,399 lines, -36.5%)
All rendering functions now properly modularized with full JSDoc documentation
Event listeners preserved in render functions for interactive fields

src/utils/avatars.js

@@ -0,0 +1,46 @@
+/**
+ * Avatar Utilities Module
+ * Handles safe avatar/thumbnail URL generation with error handling
+ */
+
+import { getThumbnailUrl } from '../../../../../../script.js';
+
+/**
+ * Safely retrieves a thumbnail URL from SillyTavern's API with error handling.
+ * Returns null instead of throwing errors to prevent extension crashes.
+ *
+ * @param {string} type - Type of thumbnail ('avatar' or 'persona')
+ * @param {string} filename - Filename of the avatar/persona
+ * @returns {string|null} Thumbnail URL or null if unavailable/error
+ */
+export function getSafeThumbnailUrl(type, filename) {
+    // Return null if no filename provided
+    if (!filename || filename === 'none') {
+        console.log(`[RPG Companion] No valid filename provided for ${type} thumbnail`);
+        return null;
+    }
+
+    try {
+        // Attempt to get thumbnail URL from SillyTavern API
+        const url = getThumbnailUrl(type, filename);
+
+        // Validate that we got a string back
+        if (typeof url !== 'string' || url.trim() === '') {
+            console.warn(`[RPG Companion] getThumbnailUrl returned invalid result for ${type}:`, filename);
+            return null;
+        }
+
+        console.log(`[RPG Companion] Successfully generated ${type} thumbnail URL for: ${filename}`);
+        return url;
+    } catch (error) {
+        // Log detailed error information for debugging
+        console.error(`[RPG Companion] Failed to get ${type} thumbnail for "${filename}":`, error);
+        console.error('[RPG Companion] Error details:', {
+            type,
+            filename,
+            errorMessage: error.message,
+            errorStack: error.stack
+        });
+        return null;
+    }
+}