feat(ai-service): complete ai production readiness tasks

Implement critical production readiness features for AI integration: per-request provider config, admin dashboard, workflow inspection, and plugin framework foundation.

Per-Request Provider Config:
- Add ProviderConfig struct to all AI request types
- Update queue to resolve provider/model/API key from cascade (repo > org > system)
- Pass resolved config to AI sidecar on every request
- Fixes multi-tenant issue where all orgs shared sidecar's hardcoded config

Admin AI Dashboard:
- Add /admin/ai page with sidecar health status
- Display global operation stats (total, 24h, success/fail/escalated counts)
- Show operations by tier, top 5 repos, token usage
- Recent operations table with repo, operation, status, duration
- Add GetGlobalOperationStats model method

Workflow Inspection:
- Add InspectWorkflow client method and types
- Implement workflow-inspect queue handler
- Add notifier trigger on workflow file push
- Analyzes YAML for syntax errors, security issues, best practices
- Returns structured issues with line numbers and suggested fixes

Plugin Framework (Phase 5 Foundation):
- Add external plugin config loading from app.ini
- Define ExternalPlugin interface and manager
- Add plugin.proto contract (Initialize, Shutdown, HealthCheck, OnEvent, HandleHTTP)
- Implement health monitoring with auto-restart for managed plugins
- Add event routing to subscribed plugins
- HTTP proxy support for plugin-served routes

This completes Tasks 1-4 from the production readiness plan and establishes the foundation for managed plugin lifecycle.

options/locale/locale_en-US.json

@@ -4619,6 +4619,16 @@
   "actions.runners.waiting_jobs": "Waiting Jobs",
   "actions.runners.back_to_runners": "Back to Runners",
   "actions.runners.no_waiting_jobs": "No jobs waiting for this label",
+  "admin.ai": "AI Status",
+  "admin.ai.title": "AI Service Status",
+  "admin.ai.sidecar_status": "Sidecar Status",
+  "admin.ai.config": "Configuration",
+  "admin.ai.stats": "Statistics",
+  "admin.ai.recent_operations": "Recent Operations",
+  "admin.ai.total_operations": "Total Operations",
+  "admin.ai.operations_24h": "Operations (24h)",
+  "admin.ai.success_rate": "Success Rate",
+  "admin.ai.tokens_used": "Tokens Used",
   "admin.ai_learning": "AI Learning",
   "admin.ai_learning.edit": "Edit Pattern",
   "admin.ai_learning.total_patterns": "Total Patterns",