fix: sync ID counters after import to prevent collisions

When importing issues with explicit high IDs (e.g., bd-100), the
issue_counters table wasn't being updated. This caused the next
auto-generated issue to collide with existing IDs (bd-4 instead of bd-101).

Changes:
- Add SyncAllCounters() to scan all issues and update counters atomically
- Add SyncCounterForPrefix() for granular counter synchronization
- Call SyncAllCounters() in import command after creating issues
- Add comprehensive tests for counter sync functionality
- Update TestImportCounterSyncAfterHighID to verify fix

The fix uses a single efficient SQL query to prevent ID collisions
with subsequently auto-generated issues.

cmd/bd/import_collision_test.go

@@ -1023,6 +1023,13 @@ func TestImportCounterSyncAfterHighID(t *testing.T) {
 		t.Fatalf("Failed to import high ID issue: %v", err)
 	}
 
+	// Step 4: Sync counters after import (mimics import command behavior)
+	if err := testStore.SyncAllCounters(ctx); err != nil {
+		t.Fatalf("Failed to sync counters: %v", err)
+	}
+
+	// Step 5: Create another auto-generated issue
+	// This should get bd-101 (counter should have synced to 100), not bd-4
 	newIssue := &types.Issue{
 		Title:     "New issue after import",
 		Status:    types.StatusOpen,