Add safe demo mode and full pipeline command

[junnaid-4]

Summary

Adds a zero-key fictional demo mode and a reusable full-pipeline command for LeadFinder CLI.

Features

• Added lead-finder demo --config config.demo.yaml
• Added a deterministic fictional dataset with 12 businesses
• Added network-free demo scoring and CSV/XLSX exports
• Implemented the full lead-finder run pipeline
• Added --format, --output-dir, --force-refresh, and --overwrite
• Extracted shared typed pipeline services
• Unified export filtering and deterministic sorting
• Removed unfinished placeholder commands

Safety

• Demo mode must be explicitly enabled in configuration
• Demo overwrite is restricted to known demo-owned paths
• Existing artifacts are preserved if regeneration fails
• CSV and XLSX are staged before pair-level replacement
• Website persistence failures now fail the pipeline
• Failed collection runs are finalized correctly
• Refreshing cached data and overwriting reports are separate options

Quality

• 150 tests passing
• Ruff linting passing
• Ruff formatting passing
• Strict MyPy passing
• Source distribution and wheel builds passing
• Installed-wheel demo execution verified

Limitations

• Live collection requires a Google Places API key and billing
• Demo data is synthetic
• SQLite is intended primarily for local, single-user operation
• No hosted dashboard or automated outreach is included