feat(doctor): add database corruption recovery to --fix

Adds automatic database recovery when bd doctor --fix detects corruption:
- Detects SQLite corruption (malformed database, SQLITE_CORRUPT errors)
- Backs up corrupted database before recovery attempt
- Rebuilds from JSONL if available (issues.jsonl, deletions.jsonl)
- Falls back to fresh database if JSONL unavailable
- Reports recovery results (issues imported, success/failure)

Recovery is triggered automatically by --fix when corruption is detected.
No manual intervention required.

cmd/bd/doctor/git.go

@@ -145,6 +145,8 @@ func CheckSyncBranchHookCompatibility(path string) DoctorCheck {
 			Status:  StatusWarning,
 			Message: "Pre-push hook is not a bd hook",
 			Detail:  "Cannot verify sync-branch compatibility with custom hooks",
+			Fix: "Either run 'bd hooks install --force' to use bd hooks,\n" +
+				"  or ensure your custom hook skips validation when pushing to sync-branch",
 		}
 	}