Fix heap buffer overflow in BundlePacket

[devin-ai-integration]

This PR fixes a heap buffer overflow in BundlePacket that was detected by AddressSanitizer.

The issue occurred when writing padding bytes without proper bounds checking. The fix:

1. Increases padding size allocation in PreparePacket to ensure enough space for worst-case scenarios
2. Adds explicit bounds checking before writing padding
3. Improves error handling and logging

Stack trace of the original issue:

==408==ERROR: AddressSanitizer: heap-buffer-overflow on address 0x507000000065
WRITE of size 11 at 0x507000000065 thread T0
    #0 0x564cf43ca334 in __asan_memset
    #1 0x564cf442e2a7 in BundlePacket wolfssh/src/internal.c:10113:13
    #2 0x564cf4444167 in SendUserAuthRequest wolfssh/src/internal.c:14868:19

Link to Devin run: https://app.devin.ai/sessions/09306447f6034de789ee35da39734150
Requested by: [email protected]

[devin-ai-integration]

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