Remove obsolete JSON format support from Live Data Server

[darshdinger]

Short description of the changes:

Removed the obsolete JSON data format option for publishing plot data. The server now only accepts HTML format data. The data_type field remains in the database model for backward compatibility but is effectively always set to 1 (HTML).

Long description of the changes:

This PR addresses issues with the fragile JSON format detection logic (the <div string check in get_data_type_from_data() method) that caused problems with REF_M data processing.

Changes made:

• Simplified DATA_TYPES constant from {"json": 0, "html": 1} to {"html": 1}
• Removed JSON upload endpoint (/update/json/)
• Removed user data endpoints (/upload_user_data/ and /list/)
• Removed get_data_type_from_data() and get_data_type_from_string() helper methods
• Simplified _store() function to always use HTML data type
• Removed store_user_data() from view utilities
• Updated tests to remove JSON and user data test cases
• Cleaned up documentation references to JSON format

The database schema remains unchanged - the data_type field is preserved to avoid migration complexity and maintain backward compatibility with existing data.

Check list for the pull request

• I have read the [CONTRIBUTING]
• I have read the [CODE_OF_CONDUCT]
• I have added tests for my changes
• I have updated the documentation accordingly

Check list for the reviewer

• I have read the [CONTRIBUTING]
• I have verified the proposed changes
• best software practices
  • all internal functions have an underbar, as is python standard
  • clearly named variables (better to be verbose in variable names)
  • code comments explaining the intent of code blocks
• All the tests are passing
• The documentation is up to date
• code comments added when explaining intent

Manual test for the reviewer

1. Start the Docker environment: docker compose up -d
2. Verify the Django container starts successfully
3. Run the test suite in the pixi environment: pixi shell then pytest
4. All 9 tests should pass (2 enum tests, 2 expiration tests, 5 post/get tests)
5. Test uploading HTML plot data:

   curl -X POST http://localhost/plots/TEST_INST/12345/upload_plot_data/ \
     -F "file=@tests/data/reflectivity.html" \
     -F "data_id=test_plot" \
     -H "Authorization: <test_key>"

6. Verify the old JSON endpoint returns 404:

   curl http://localhost/plots/TEST_INST/12345/update/json/

References

• Related to REF_M data processing issues caused by fragile <div string detection
• EWM Work Item: EWM # 14160

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 85.15%. Comparing base (efdf308) to head (ba8edb0).

Additional details and impacted files

@@            Coverage Diff             @@
##             next      #57      +/-   ##
==========================================
- Coverage   89.97%   85.15%   -4.82%     
==========================================
  Files          12       12              
  Lines         359      283      -76     
==========================================
- Hits          323      241      -82     
- Misses         36       42       +6     

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