Add bounds checking to prevent buffer overflow in bitmap access

- Add safety check in allocPage() before accessing pageBitmap
- Add safety check in freePage() before accessing pageBitmap
- Prevents potential buffer overflow when bitmap size limits are reached

Co-authored-by: johndoe6345789 <224850594+johndoe6345789@users.noreply.github.com>

kernel/src/memory.cpp

@@ -74,6 +74,11 @@ void* PhysicalMemoryManager::allocPage() {
         uint64_t byte = i / 8;
         uint64_t bit = i % 8;
         
+        // Bounds check to prevent buffer overflow
+        if (byte >= BITMAP_SIZE) {
+            break;
+        }
+        
         if (!(pageBitmap[byte] & (1 << bit))) {
             // Mark as used
             pageBitmap[byte] |= (1 << bit);
@@ -111,6 +116,11 @@ void PhysicalMemoryManager::freePage(void* page) {
     uint64_t byte = pageIdx / 8;
     uint64_t bit = pageIdx % 8;
     
+    // Bounds check to prevent buffer overflow
+    if (byte >= BITMAP_SIZE) {
+        return;
+    }
+    
     // Mark as free
     pageBitmap[byte] &= ~(1 << bit);
     usedPages--;