Restrict Spring AI tool execution to request callbacks (OWASP LLM06)

Disable explicit true or Boolean.TRUE arguments to DefaultToolCallingManager.Builder.resolutionFallbackEnabled and direct true Spring configuration values. This prevents resolver fallback from executing tools absent from the request callbacks. Dynamic expressions, placeholders, and missing settings are preserved. Applications intentionally using fallback must attach required callbacks to requests before adopting this policy. Does not remove explicitly attached tools or provide authorization for their execution.