Fix multiple bugs found during code review

[jgowdy-godaddy]

Summary

• Fix Setup() race condition: Replace Load+Store with CompareAndSwap to prevent concurrent initialization overwriting globalSessionFactory. Roll back initialized flag on factory creation failure.
• Fix wrong variable in error log: SetupJson line 84 logged result (from BufferToJsonStruct) instead of stringResult (from BufferToString)
• Fix panic re-throw in FFI exports: All exported functions were catching panics then re-panicking, which is undefined behavior across an FFI boundary. Now returns ERR_PANIC (-106) via named return values instead.
• Make DisableZeroCopy atomic: Was a plain bool written in SetupJson and read in encryptData — data race under -race. Now uses atomic.Bool.
• Close DB connection in Shutdown: dbconnection was opened but never closed, leaking the resource.
• Add missing log in Decrypt not-initialized: Encrypt logged "not initialized" but Decrypt returned silently. Now consistent.
• Check os.Setenv errors in SetEnv: Previously silently ignored failures. Now logs and returns ERR_BAD_CONFIG.

Test plan

• All 32 tests pass
• go vet clean
• go build clean