safety: harden SOS honesty and fallback behavior

[NITISH-R-G]

Description

Harden the emergency flow to be more honest and reliable under accident conditions.

• remove the fake "nearby responder" success path and mark it as not configured
• carry crash severity hints from crash detection into triage/validation
• enforce a real Tier 4 keyword fallback after Tier 3 failures
• persist a local incident receipt even on the no-GPS branch
• relabel first-aid guidance to remove misleading medical certainty and localize the touched screen
• add a README feature-status section and correct several overstated product claims
• make AI triage status copy honest even when the cloud tier is skipped

Fixes # (issue)

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update

How Has This Been Tested?

Please describe the tests that you ran to verify your changes.

• Unit Tests
• Integration Tests
• Manual Smoke Test (on physical device)

Commands run:

• flutter gen-l10n
• flutter analyze
• flutter test

Notes:

• flutter analyze passed.
• flutter test passed (17 tests).
• Flutter emitted existing upstream warnings about flutter_blue_plus referencing a missing Windows default plugin package (flutter_blue_plus_winrt), but the app still analyzed and tested successfully in this environment.
• Localization generation still reports many untranslated non-English strings already present in the repo; this branch only localized the touched first-aid copy and neutralized the AI status message.

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