Add IN_433 regulatory region code

[kholia]

What does this PR do?

Append IN_433 as RegionCode 38 without renumbering existing values. This prepares generated bindings and firmware support for India's 433.05-434.79 MHz allocation under G.S.R. 347(E), 2022.

Regulatory source: https://eservices.dot.gov.in/sites/default/files/circular-notifications/the-use-of-low-power-radio-frequency-devices-in-the-frequency-band-433.05-to-434.79-mhz-exemption-from-license-rules-2022.pdf

Current DoT spectrum-plan context: https://www.dot.gov.in/static/uploads/2026/02/52e468605d5b63c6dfedcf538f1d7d36.pdf

Related firmware context: meshtastic/firmware#5940

Checklist before merging

• All top level messages commented
• All enum members have unique descriptions

Summary by CodeRabbit

• New Features
  • Added support for the India 433 MHz regional configuration.
  • Included documentation for the new regional option.

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ℹ️ Recent review info

⚙️ Run configuration

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Review profile: CHILL

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Run ID: 47433e64-6d67-4085-81b6-6a282709ddc4

📥 Commits

Reviewing files that changed from the base of the PR and between 4224473 and 93c5b63.

📒 Files selected for processing (1)

• meshtastic/config.proto

🚧 Files skipped from review as they are similar to previous changes (1)

• meshtastic/config.proto

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📝 Walkthrough

Walkthrough

Adds the documented IN_433 = 38 value to LoRaConfig.RegionCode in meshtastic/config.proto.

Changes

LoRa region code update

Layer / File(s)	Summary
Add India 433MHz region code meshtastic/config.proto	LoRaConfig.RegionCode now includes the documented IN_433 = 38 enum value.

Estimated code review effort: 1 (Trivial) | ~2 minutes

Possibly related PRs

• meshtastic/protobufs#985: Modifies the same LoRaConfig.RegionCode enum and uses numeric code 38.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title is concise and accurately summarizes the main change: adding the IN_433 region code.
Description check	✅ Passed	The description includes the required PR purpose section and checklist, and it clearly explains the regulatory change.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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