Replace the in-memory nextID counter with an atomic database-backed
counter using the issue_counters table. This fixes race conditions
when multiple processes create issues concurrently.
Changes:
- Add issue_counters table with atomic INSERT...ON CONFLICT pattern
- Remove in-memory nextID field and sync.Mutex from SQLiteStorage
- Implement getNextIDForPrefix() for atomic ID generation
- Update CreateIssue() to use database counter instead of memory
- Update RemapCollisions() to use database counter for collision resolution
- Clean up old planning and bug documentation files
Fixes the multi-process ID generation race condition tested in
cmd/bd/race_test.go.
20e3235435