docs(medic/cht-core#10357): document LOG_LEVEL env variable for Docker deployments

[sugat009]

Summary

• Documents the LOG_LEVEL environment variable for controlling log verbosity in api and sentinel containers
• Recommends the .env file approach (consistent with CHT deployment conventions) instead of shell export
• Clarifies that docker compose up -d (not docker compose restart) is required to pick up env var changes
• Notes that from CHT 5.1.0 onward, NODE_ENV no longer affects logging detail

Supersedes #2030 (taking over from @AmirSaudagar55).

Linked issue

medic/cht-core#10357

Test plan

• Verify the "Setting log level" section renders correctly
• Confirm supported log level values match Winston logger defaults in shared-libs/logger/src/node-logger.js
• Confirm .env file approach is consistent with existing CHT Docker deployment docs

[sugat009]

@jkuester I created another PR to make a few changes w.r.t. medic/cht-core#10583. Would appreciate a review. Thanks!

[jkuester]

LGTM!

[jkuester]

Minor, but it seems a bit confusing to put "production use" here and then also say "recommended for production" below for info. Probably okay to just remove the "production use" from this one... 🤷