docs(contract): add comprehensive contract error documentation table (#710)

[ravendevhub]

Summary

Resolves #710 by creating a comprehensive reference table in docs/CONTRACT_ERROR_TABLE.md documenting all public Soroban #[contracterror] error codes, trigger conditions, and expected caller recovery/remediation behaviour.

Changes

1. Contract Error Reference (docs/CONTRACT_ERROR_TABLE.md):
   • Documents all 39 error codes defined in contract/contracts/hello-world/src/base/errors.rs.
   • Explains root trigger conditions (e.g. invalid percentages, paused state, unauthorized callers, zero-address transfers).
   • Provides clear caller resolution instructions.
2. Client Handling Guidelines:
   • Outlines how off-chain listeners and dashboard interfaces should handle host simulation error codes.

Acceptance Criteria

• All public contract errors are documented.
• Error identifiers and meanings are listed.
• Conditions that trigger each error are described.
• Documentation matches the current contract implementation.