fix(templates): add input validation, callable checks, and cycle tracing in _runtime_dependency_order

[Vishaaallll]

Summary

Adds strict input type validation and defensive error handling for service dependency resolution in _runtime_dependency_order() in ods/extensions/services/dashboard-api/routers/templates.py:

• Validates that service_id is a non-empty string.
• Verifies read_direct_deps parameter is callable and returns iterable collections (list, tuple, set).
• Skips non-string or whitespace-only dependency entries during iteration.
• Encloses recursive dependency traversal in a try...finally block to guarantee _visiting set cleanup even when exceptions occur.
• Enriches circular dependency error detail by formatting the full cycle path (e.g., service_a -> service_b -> service_a).

Why It Is Useful

• Prevents State Leakage & Cascading Failures: Standardizes recursion cleanup in _visiting state so subsequent requests do not fail due to lingering stack frames when errors occur during dependency resolution.
• Hardens API Resilience: Guards against unhandled server exceptions when custom extension manifests contain unexpected schema structures or null dependency elements.
• Improves Operator Diagnostics: Provides explicit, formatted cycle chains in error responses for faster troubleshooting of template configuration issues.

Verification

• Ran test suite pytest ods/extensions/services/dashboard-api/tests/test_templates.py -v (31 passed).