feat(inventory): granular item-level validation and auto-capitalization

Enhances validation to clean corrupted items at load time while preserving
valid ones, rather than discarding entire sections. Also auto-capitalizes
first letter of items for consistency.

New capability - Granular Item Cleaning:

1. **cleanItemString()** (src/utils/security.js):
   - Parses item string, removes bad items, re-serializes clean ones
   - Applies ALL parsing rules: markdown, sanitization, length limits
   - Used at load time to clean persisted data immediately
   - Returns "None" if no valid items remain

2. **Enhanced validateStoredInventory()**:
   - Now cleans items within each location
   - Only removes locations if ALL items are invalid
   - Example: "Home": "Sword, __proto__, Shield" → "Home": "Sword, Shield"
   - Example: "Bad": "__proto__, constructor" → location removed

3. **Enhanced validateInventoryStructure()** (src/core/persistence.js):
   - Cleans onPerson, stored, and assets at load time
   - Logs exactly what was cleaned for debugging
   - Auto-saves cleaned data back to storage

Auto-Capitalization:

- Added to cleanSingleItem() in itemParser.js
- Capitalizes first letter of each item after all cleaning
- Preserves rest of case: "iPhone" → "iPhone" (not "Iphone")
- Examples: "sword" → "Sword", "3x potions" → "3x potions"

Behavior examples:

Before (threw away entire array):
- "Home": "Sword, " + "A".repeat(600) + ", Shield"
  → Entire location lost

After (granular cleaning):
- "Home": "Sword, " + "A".repeat(600) + ", Shield"
  → "Home": "Sword, AAA...(500 chars), Shield"

Before (kept corrupted data):
- onPerson: "sword, __proto__, shield"
  → Stored as-is, filtered only at render

After (cleaned at load):
- onPerson: "Sword, Shield"
  → Cleaned and saved immediately, capitalized

Benefits:
- ✓ Preserves valid items when some are corrupted
- ✓ Cleans data at source, not just at render
- ✓ Detailed logging of what was cleaned
- ✓ Consistent capitalization across all items
- ✓ Single source of truth for "valid item"

src/utils/itemParser.js

@@ -187,7 +187,7 @@ export function parseItems(itemString) {
 
 /**
  * Cleans a single item string (helper for parseItems)
- * Removes list markers, wrapping quotes, and trims
+ * Removes list markers, wrapping quotes, trims, and capitalizes first letter
  *
  * @param {string} item - Single item string to clean
  * @returns {string|null} Cleaned item or null if empty/invalid
@@ -222,6 +222,12 @@ function cleanSingleItem(item) {
         return null;
     }
 
+    // Capitalize first letter for consistency
+    // Preserves rest of string case (e.g., "iPhone" stays "iPhone", not "Iphone")
+    if (cleaned.length > 0) {
+        cleaned = cleaned.charAt(0).toUpperCase() + cleaned.slice(1);
+    }
+
     return cleaned;
 }