feat(workflows): add full Workflow section — visual constructor, dashboard & execution engine

## New Feature: Workflow Builder & Execution Engine

### Database Schema (4 new tables)
- workflows: pipeline definitions with status (draft/active/paused/archived), tags, canvas metadata
- workflowNodes: agent/container/trigger/condition/output blocks with canvas positions
- workflowEdges: directional connections between nodes (source→target)
- workflowRuns: execution history with per-node status tracking & timing

### Backend (server/workflows.ts + 13 tRPC endpoints in routers.ts)
- Full CRUD for workflows, nodes, edges
- Atomic canvas save (nodes + edges in one mutation)
- BFS graph execution engine: walks from trigger nodes, executes agents/containers in order
- Single-node test execution for individual block testing
- Run management: start, cancel, poll status, list history
- Aggregated workflow stats (success rate, avg duration, run counts)

### Frontend — Visual Constructor
- WorkflowCanvas: interactive drag-and-drop builder with:
  - Node palette sidebar (trigger/agent/container/condition/output types)
  - Agent list for quick drag-to-canvas agent nodes
  - Edge drawing between output→input ports with bezier curves
  - Pan/zoom controls + grid background
  - Keyboard shortcuts (Delete, Ctrl+S)
  - Real-time run status overlays (running/success/failed per node)
- WorkflowNodeBlock: kind-aware visual cards with status indicators & connection ports
- WorkflowNodeEditModal: per-kind configuration (agent selector, Docker image/env, condition expressions, cron/webhook triggers)
- WorkflowCreateModal: create new workflows with name, description, tags
- WorkflowDashboard: monitoring panel with stats cards, run history timeline, per-node progress bars
- Workflows page: unified list/canvas/dashboard views with tabs

### Navigation & Routing
- Added Workflows nav item (GitBranch icon) in sidebar between Agents and Tools
- Routes: /workflows (list), /workflows/:id (dashboard+canvas)

### Also includes
- fix(nodes): keep AddNodeDialog open after join + canJoin guard

drizzle/0007_workflows.sql

@@ -0,0 +1,77 @@
+-- Workflows: pipeline definitions
+CREATE TABLE `workflows` (
+	`id` int AUTO_INCREMENT NOT NULL,
+	`name` varchar(255) NOT NULL,
+	`description` text,
+	`status` enum('draft','active','paused','archived') NOT NULL DEFAULT 'draft',
+	`canvasMeta` json DEFAULT ('{}'),
+	`tags` json DEFAULT ('[]'),
+	`createdBy` int,
+	`createdAt` timestamp NOT NULL DEFAULT (now()),
+	`updatedAt` timestamp NOT NULL DEFAULT (now()) ON UPDATE CURRENT_TIMESTAMP,
+	CONSTRAINT `workflows_id` PRIMARY KEY(`id`)
+);
+--> statement-breakpoint
+
+-- Workflow Nodes: blocks inside a workflow (agent / container / trigger / condition / output)
+CREATE TABLE `workflowNodes` (
+	`id` int AUTO_INCREMENT NOT NULL,
+	`workflowId` int NOT NULL,
+	`nodeKey` varchar(64) NOT NULL,
+	`label` varchar(255) NOT NULL,
+	`kind` enum('agent','container','trigger','condition','output') NOT NULL,
+	`agentId` int,
+	`containerConfig` json DEFAULT ('{}'),
+	`conditionExpr` text,
+	`triggerConfig` json DEFAULT ('{}'),
+	`posX` int DEFAULT 0,
+	`posY` int DEFAULT 0,
+	`meta` json DEFAULT ('{}'),
+	`createdAt` timestamp NOT NULL DEFAULT (now()),
+	`updatedAt` timestamp NOT NULL DEFAULT (now()) ON UPDATE CURRENT_TIMESTAMP,
+	CONSTRAINT `workflowNodes_id` PRIMARY KEY(`id`)
+);
+--> statement-breakpoint
+CREATE INDEX `workflowNodes_workflowId_idx` ON `workflowNodes` (`workflowId`);
+--> statement-breakpoint
+
+-- Workflow Edges: connections between nodes
+CREATE TABLE `workflowEdges` (
+	`id` int AUTO_INCREMENT NOT NULL,
+	`workflowId` int NOT NULL,
+	`edgeKey` varchar(64) NOT NULL,
+	`sourceNodeKey` varchar(64) NOT NULL,
+	`targetNodeKey` varchar(64) NOT NULL,
+	`sourceHandle` varchar(64),
+	`targetHandle` varchar(64),
+	`label` varchar(128),
+	`meta` json DEFAULT ('{}'),
+	`createdAt` timestamp NOT NULL DEFAULT (now()),
+	CONSTRAINT `workflowEdges_id` PRIMARY KEY(`id`)
+);
+--> statement-breakpoint
+CREATE INDEX `workflowEdges_workflowId_idx` ON `workflowEdges` (`workflowId`);
+--> statement-breakpoint
+
+-- Workflow Runs: execution history with per-node results
+CREATE TABLE `workflowRuns` (
+	`id` int AUTO_INCREMENT NOT NULL,
+	`workflowId` int NOT NULL,
+	`runKey` varchar(64) NOT NULL,
+	`status` enum('pending','running','success','failed','cancelled') NOT NULL DEFAULT 'pending',
+	`nodeResults` json DEFAULT ('{}'),
+	`currentNodeKey` varchar(64),
+	`input` text,
+	`output` text,
+	`totalDurationMs` int,
+	`errorMessage` text,
+	`startedAt` timestamp,
+	`finishedAt` timestamp,
+	`createdAt` timestamp NOT NULL DEFAULT (now()),
+	CONSTRAINT `workflowRuns_id` PRIMARY KEY(`id`),
+	CONSTRAINT `workflowRuns_runKey_unique` UNIQUE(`runKey`)
+);
+--> statement-breakpoint
+CREATE INDEX `workflowRuns_workflowId_idx` ON `workflowRuns` (`workflowId`);
+--> statement-breakpoint
+CREATE INDEX `workflowRuns_status_idx` ON `workflowRuns` (`status`);