Add database size and storage metrics to `health` command

[roeimichael]

Problem

The health command shows event and snapshot counts but not the database file size, per-table row counts, or schema version. Users with long retention periods have no visibility into how much disk space CAT is consuming.

What to do

Enhance the /api/health endpoint and CLI health command to include:

1. Database file size — Path(db_path).stat().st_size (format as human-readable KB/MB)
2. Per-table row counts — use the existing get_table_counts() from src/context_analyzer_tool/db/maintenance.py
3. Schema version — use get_schema_version() from src/context_analyzer_tool/db/schema.py

Files to look at

• src/context_analyzer_tool/collector/routes.py — /api/health endpoint
• src/context_analyzer_tool/collector/models.py — HealthResponse model (add fields)
• src/context_analyzer_tool/cli.py — health command output
• src/context_analyzer_tool/db/maintenance.py — get_table_counts() already exists

Why this is a good first issue

Uses existing helper functions — just wire them into the health response and display. Small, well-scoped change.