refactor: rename action→activity, statemachine→workflow, remove HTTP API layer

- action/ → activity/ (Temporal activities)
- statemachine/ → workflow/ (Temporal workflows)
- Removed internal/api/ and cmd/server/ (api-gw handles HTTP, Temporal is the API)
- Created pkg/types/types.go as single source of truth for all shared types
- Extracted CallRoleLLM helper (DRY: implementer/planner/judge shared pattern)
- Fixed circular import: workflow_graph_query uses string activity names
- Fixed logger.logf → logger.Info/Warn (method didn't exist)
- Fixed routing types: added Branches, Activity, BackoffSeconds, TaskActivity
- Fixed db.Canvas.Name, db.Client→DB, GetWorkflow→FetchWorkflow
- Removed unused imports
- All tests pass, build clean, vet clean

tests/temporal_routing_test.go

@@ -9,7 +9,7 @@ import (
 	"time"
 
 	"github.com/rockliang/poimen/workflows/internal/routing"
-	"github.com/rockliang/poimen/workflows/statemachine"
+	"github.com/rockliang/poimen/workflows/workflow"
 	"github.com/stretchr/testify/require"
 	"go.temporal.io/sdk/client"
 )
@@ -69,12 +69,12 @@ func TestTemporalRoutingWorkflow(t *testing.T) {
 
 		// Submit to Temporal
 		workflowID := "test-routing-" + time.Now().Format("20060102-150405")
-		input := statemachine.RoutingWorkflowInput{Spec: output.Spec}
+		input := workflow.RoutingWorkflowInput{Spec: output.Spec}
 
 		run, err := c.ExecuteWorkflow(ctx, client.StartWorkflowOptions{
 			ID:        workflowID,
 			TaskQueue: "poimen-taskqueue",
-		}, statemachine.RoutingWorkflow, input)
+		}, workflow.RoutingWorkflow, input)
 		require.NoError(t, err)
 
 		t.Logf("Workflow submitted: ID=%s, RunID=%s", run.GetID(), run.GetRunID())
@@ -118,18 +118,18 @@ func TestTemporalRoutingWorkflow(t *testing.T) {
 		}
 
 		workflowID := "test-pass-only-" + time.Now().Format("20060102-150405")
-		input := statemachine.RoutingWorkflowInput{Spec: spec}
+		input := workflow.RoutingWorkflowInput{Spec: spec}
 
 		run, err := c.ExecuteWorkflow(ctx, client.StartWorkflowOptions{
 			ID:        workflowID,
 			TaskQueue: "poimen-taskqueue",
-		}, statemachine.RoutingWorkflow, input)
+		}, workflow.RoutingWorkflow, input)
 		require.NoError(t, err)
 
 		t.Logf("Pass-only workflow submitted: ID=%s", run.GetID())
 
 		// Wait for result (Pass states don't need workers)
-		var result statemachine.RoutingWorkflowOutput
+		var result workflow.RoutingWorkflowOutput
 		err = run.Get(ctx, &result)
 		require.NoError(t, err)