Add context-aware vacancy moderation

[iamwavecut]

Summary

• correct the semantic boundary so recruiter contacts and explicit application prompts do not make detailed vacancies spam
• add per-chat General and Jobs & HR moderation profiles plus separately labeled allowed and spam examples
• expose the new controls in the private admin panel with complete locale coverage and a backward-compatible SQLite migration

Verification

• go test ./...
• go test -race ./...
• go test -shuffle=on ./...
• go vet ./...
• configured golangci-lint
• go mod tidy -diff
• go tool govulncheck ./...
• Docker build
• live Gemini 2.5 Flash Lite semantic checks in General and Jobs & HR profiles: detailed PM vacancy with Напишите Привет, detailed iGaming vacancy, and vague high-income solicitation