ISSUE-4341: Allow more legal Sub-GHz frequencies in Germany

[herbenderbler]

Summary

This PR expands the EU/RU Sub-GHz regulatory band table to include additional legal frequencies requested for Germany.

Problem

The current EU/RU region limits in firmware did not include:

• 868.7–869.2 MHz (commonly used by some garage remotes in Germany, including around 868.8 MHz)
• The broader 868.0–868.6 MHz span (instead of only 868.15–868.55 MHz)

As a result, legal frequencies requested in the original feature report were not covered by the EU/RU region band definitions.

Original feature request: #4341

What's changed?

Updated EU/RU region bands in targets/f7/furi_hal/furi_hal_region.c:

• Changed EU/RU bands_count from 2 to 3
• Replaced:
  • 868150000–868550000
• With:
  • 868000000–868600000
  • 868700000–869200000

No app UI frequency list changes were made in this PR.
No unrelated logic changes were made.

Validation and testing performed

1) Build validation

• Built firmware successfully:
  • ./fbt
• Verified changed file compiled with no diagnostics errors.

2) Device flashing and packaging validation

• First flashed with:
  • ./fbt flash_usb
• Then flashed full package (to ensure external apps/resources are installed):
  • ./fbt flash_usb_full
• Verified About screen reflects local build metadata after flashing.

3) On-device CLI RX tuning validation (new ranges)

Executed on physical device CLI with internal radio (device 0):

• subghz rx 868000000 0
• subghz rx 868600000 0
• subghz rx 868700000 0
• subghz rx 868800000 0
• subghz rx 869200000 0

Observed result for each:

• Command entered listening mode successfully
• Example tuned values reported by hardware synthesizer quantization:
  • 867999938
  • 868599792
  • 868699768
  • 868799743
  • 869199645
• Packets received remained 0 during short test windows (expected in quiet RF environment)

4) Region policy behavior check (TX on US-region hardware)

Executed:

• subghz tx 74BADE 868800000 403 2 0

Observed:

• Transmission on this frequency is restricted in your region

This confirms expected behavior on US-region hardware:

• RX tuning can occur
• TX remains blocked by active regional policy

Follow-up (debug helper only)

As a small follow-up, this branch also updates the debug Sub-GHz test frequency helper to include representative values from the newly added 868 MHz ranges. This is limited to debug tooling and does not change runtime region policy behavior or user-facing regulatory logic.

• Updated applications/debug/subghz_test/helpers/subghz_test_frequency.c to add:
  • 868000000
  • 868600000
  • 868700000
  • 868800000
  • 869200000
• Frequency list order is preserved (ascending).
• File-level diagnostics check reports no errors.

Notes

This PR updates EU/RU regulatory band definitions only.
It does not alter region provisioning behavior, and it does not bypass regional TX policy enforcement.

Checklist (For Reviewer)

• PR has description of feature/bug or link to Confluence/Jira task
• Description contains actions to verify feature/bugfix
• I've built this code, uploaded it to the device and verified feature/bugfix