Fix Cursor provider dropping data older than 35 days

[iamtoruk]

Summary

• Increase the Cursor parseBubbles lookback from 35 to 180 days so longer period views (30-day, month, all) surface historical data
• The hardcoded 35-day floor silently dropped all bubbles older than 5 weeks, making --period all return $0
• NULL createdAt handling (OR IS NULL in SQL, fallback timestamp) was already fixed in 0.9.2
• Period scoping is handled downstream by parseProviderSources; the cursor-cache prevents repeated full DB scans

Fixes #159, fixes #163

Test plan

• 374 tests pass
• TypeScript type check clean