docs: Add inline code examples to all existing tutorials

[nanaf6203-bit]

Description

The tutorials in docs/tutorials/ are mostly text descriptions. Add working code examples that readers can copy and run.

Acceptance Criteria

• Update basic-property-registration.md with code examples for each step
• Update property_token_tutorial.md with Rust code snippets
• Update escrow-system.md with complete escrow workflow examples
• Update cross-chain-bridging.md with bridge code examples
• Update ai-valuation-tutorial.md with oracle interaction examples
• Update insurance-integration.md with policy creation and claims examples
• All code examples are tested and compilable
• Add CI check that extracts and compiles tutorial code examples