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

activity/logger.go

@@ -0,0 +1,49 @@
+package activity
+
+import (
+	"context"
+	"log"
+
+	"go.temporal.io/sdk/activity"
+)
+
+// activityLogger provides logging that works both in and outside Temporal context
+type activityLogger struct {
+	ctx context.Context
+}
+
+func newActivityLogger(ctx context.Context) *activityLogger {
+	return &activityLogger{ctx: ctx}
+}
+
+func (l *activityLogger) Info(msg string, args ...interface{}) {
+	if activity.IsActivity(l.ctx) {
+		activity.GetLogger(l.ctx).Info(msg, args...)
+	} else {
+		log.Printf("INFO: "+msg+" %v", args)
+	}
+}
+
+func (l *activityLogger) Warn(msg string, args ...interface{}) {
+	if activity.IsActivity(l.ctx) {
+		activity.GetLogger(l.ctx).Warn(msg, args...)
+	} else {
+		log.Printf("WARN: "+msg+" %v", args)
+	}
+}
+
+func (l *activityLogger) Error(msg string, args ...interface{}) {
+	if activity.IsActivity(l.ctx) {
+		activity.GetLogger(l.ctx).Error(msg, args...)
+	} else {
+		log.Printf("ERROR: "+msg+" %v", args)
+	}
+}
+
+func (l *activityLogger) Debug(msg string, args ...interface{}) {
+	if activity.IsActivity(l.ctx) {
+		activity.GetLogger(l.ctx).Debug(msg, args...)
+	} else {
+		log.Printf("DEBUG: "+msg+" %v", args)
+	}
+}