feat(i18n): prompt language injection for all agents (#1327)

[mrveiss]

Summary

• Extract resolve_language() and get_language_instruction() to prompt_manager.py as shared utilities
• Add _get_localized_system_prompt() to StandardizedAgent base class — inherited by 7 agent subclasses
• Wire language injection into ChatAgent, Conversation handler, and LLMHandlerMixin
• English (default) adds no extra instruction; non-English appends a Language Requirement block
• Resolution priority: per-request param > personality profile > 'en'

Test Plan

• Set personality language to "es" → all agents respond in Spanish
• Default (no language set) → no extra instruction in prompt (no noise)
• Per-request language override works across agent types
• Verify English default adds no Language Requirement block

Closes #1327

[github-actions]

⚠️ SSOT Configuration Compliance: Violations Found

Metric	Count
Total Violations	371
SSOT Violations (high priority)	286
Other Violations	85

⚠️ 286 values have SSOT config equivalents!

These should be replaced with SSOT config imports:

Python:

from src.config.ssot_config import config
# Use: config.vm.main, config.port.backend, config.backend_url

TypeScript:

import config from '@/config/ssot-config'
// Use: config.vm.main, config.port.backend, config.backendUrl

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