FIX : Improves Ollama request robustness in textToJSON.main_loop

[Aryama-srivastav]

Description

This PR improves Ollama request robustness in textToJSON.main_loop by handling request failures explicitly instead of letting raw networking exceptions propagate.

What changed

• Added timeout to Ollama POST requests.
• Added request failure handling for requests.exceptions.RequestException.
• Added explicit error handling for non-JSON responses.
• Added response schema validation to ensure the expected "response" key exists before use.

Why

Previously, when OLLAMA_HOST was unreachable, the code surfaced raw requests/urllib3 stack traces. With this change, the backend now raises a clear, controlled RuntimeError with actionable context (target Ollama URL and failure reason), improving reliability and debugging experience.

Fixes #169

Type of change

• Bug fix (non-breaking change which fixes an issue)

How Has This Been Tested?

• Test A (repro path):
  Set:
  PYTHONPATH=src
  OLLAMA_HOST=http://127.0.0.1:18080 (unreachable host)
  Run:
  python -c "from backend import textToJSON; try: textToJSON('employee is John', ['Employee name']); except Exception as e: print(type(e).name); print(e)"

Result:
RuntimeError
Message starts with Failed to reach Ollama at http://127.0.0.1:18080/api/generate: ...

• Test B (regression intent):
  Verified that failure is now raised from application code as a controlled exception, rather than uncaught raw requests.exceptions.ConnectionError.

Test Configuration:

• Firmware version: N/A
• Hardware: Windows laptop (local)
• SDK: N/A
• Python: 3.13
• Shell: PowerShell

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules