Add --show-all-paths flag to bd dep tree

Implements bd-9: Allow users to view all paths through diamond dependencies
without deduplication. Useful for debugging complex dependency structures.

Changes:
- Added --show-all-paths flag to bd dep tree command
- Updated GetDependencyTree interface to accept showAllPaths parameter
- Modified deduplication logic to be conditional on flag
- Updated tests to pass new parameter

Amp-Thread-ID: https://ampcode.com/threads/T-43807dd5-8732-49ad-a839-cdb5dae70c35
Co-authored-by: Amp <amp@ampcode.com>

internal/storage/sqlite/dependencies_test.go

@@ -206,7 +206,7 @@ func TestGetDependencyTree(t *testing.T) {
 	store.AddDependency(ctx, &types.Dependency{IssueID: issue3.ID, DependsOnID: issue2.ID, Type: types.DepBlocks}, "test-user")
 
 	// Get tree starting from issue3
-	tree, err := store.GetDependencyTree(ctx, issue3.ID, 10)
+	tree, err := store.GetDependencyTree(ctx, issue3.ID, 10, false)
 	if err != nil {
 		t.Fatalf("GetDependencyTree failed: %v", err)
 	}