feat(humanitarian): multi-language verification prompts (#1201)

[chidii]

Closes #1201

Summary

Adds multi-language support to humanitarian verification prompts so
non-English aid claims are no longer evaluated by an English-only prompt.

Changes

• humanitarian_prompt.py: language-keyed templates, module-level detect_language(), <<MARKER>> substitution so the JSON schema survives rendering
• prompt_registry.py: VerificationPrompt ABC + version-keyed PromptRegistry
• humanitarian_verification.py: accept language param, auto-detect when absent, return language / prompt_version
• schemas/humanitarian.py: optional language field on request
• api/v1/humanitarian.py: thread language through the cached wrapper
• fixtures/humanitarian_prompts_i18n.json: golden fixtures for en/es/fr/ar
• tests/test_humanitarian_prompt_i18n.py: parametrized regression tests

Acceptance criteria

• Prompt builder accepts a language parameter
• Language detection or explicit hint determines the variant
• Each supported language has a registered, versioned prompt
• Regression fixture set per language

[Cedarich]

Doing a repo-wide cleanup - closing all currently open pull requests to reset the board, not a judgement on this contribution.

Nothing is lost: this branch and every commit on it still exist, and you're welcome to reopen this PR (or open a fresh one) at any time. If this was tracking an issue, that issue is being unassigned so it goes back into the open pool - feel free to comment on it to pick the work back up.

Thanks for contributing to Soter.