fix: add timeouts to curl commands in demo scripts

[boffin-dmytro]

Summary

Adds timeout parameters to all curl commands in demo and showcase scripts to prevent indefinite hanging.

Changes

• scripts/first-boot-demo.sh: Add --max-time 10 to health checks, --max-time 30 to LLM inference calls
• scripts/showcase.sh: Add --max-time 10 to health checks, --max-time 30 to LLM inference calls

Problem Solved

Demo scripts could hang indefinitely when:

• Services are slow to respond
• Network connections are unstable
• LLM inference takes longer than expected
• Services are completely unresponsive

Benefits

• Better UX: Scripts fail fast instead of hanging forever
• Predictable behavior: Users know when something is wrong within 10-30 seconds
• Resource efficiency: Doesn't waste time waiting for unresponsive services

Timeout Strategy

• Health checks: 10 seconds (quick service availability check)
• LLM inference: 30 seconds (allows time for model generation)

Aligns with timeout patterns used in other operational scripts like validate.sh and dream-preflight.sh.