fix(sdk): harden QR/Aruco APIs and detection wrappers

[JoDavidsson]

Summary

This PR fixes multiple reliability and memory-safety issues in Posemesh SDK QR/Aruco detection and C/Web wrappers.

Fixes

• Fix C API heap corruption risk in landmark-observation buffer allocation/layout.
• Fix invalid sentinel loop in ArUco free path.
• Fix WASM vector leaks in Web QR/Aruco landmark-observation wrappers.
• Add QR detection robustness fallback from multi decode to single decode.
• Add output-size consistency guards before observation corner indexing.
• Harden portal short-id extraction to match case-insensitive prefix search behavior.
• Add null/edge-case handling in C wrappers (Config, PoseEstimation, CalibrationHelpers, QR/Aruco).

Validation

• Ran SDK code generation in sdk/gentool.
• Ran clang++ -fsyntax-only checks on modified C/C++ wrapper files.
• Ran node --check on modified Web JS bindings.

Notes

• This PR intentionally contains only bug fixes (no new calibration feature work).

[CLAassistant]

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you sign our Contributor License Agreement before we can accept your contribution.
_{You have signed the CLA already but the status is still pending? Let us recheck it.}