Extract shared run logic to eliminate cron/manual duplication

[jluk]

Problem

src/app/api/cron/run/route.ts and src/app/api/run/route.ts duplicate ~80 lines of identical logic: source fetching, dedup, Gemini analysis, findings insert, run status update. When one gets updated, the other drifts.

Goal

Extract a shared executeRun() function in src/lib/run-competitor.ts that both routes call. Each route only handles its own concerns (auth, request parsing, response format).

Scope

• New src/lib/run-competitor.ts with shared run logic
• Simplify both API routes to thin wrappers
• Update tests accordingly