feat: integrate platform backend and application interfaces

server/migrations/0014_v1_task_dispatch_outbox.sql

@@ -0,0 +1,18 @@
+ALTER TABLE generation_tasks
+  ADD COLUMN IF NOT EXISTS task_snapshot JSONB NOT NULL DEFAULT '{}'::jsonb;
+
+CREATE TABLE IF NOT EXISTS task_dispatch_outbox (
+  task_id UUID PRIMARY KEY REFERENCES generation_tasks(id) ON DELETE CASCADE,
+  status TEXT NOT NULL DEFAULT 'pending'
+    CHECK (status IN ('pending', 'leased', 'sent', 'failed')),
+  available_at TIMESTAMPTZ NOT NULL DEFAULT now(),
+  attempts INTEGER NOT NULL DEFAULT 0,
+  lease_owner TEXT,
+  lease_expires_at TIMESTAMPTZ,
+  last_error TEXT,
+  dispatched_at TIMESTAMPTZ,
+  created_at TIMESTAMPTZ NOT NULL DEFAULT now()
+);
+
+CREATE INDEX IF NOT EXISTS task_dispatch_outbox_poll_idx
+  ON task_dispatch_outbox(status, available_at);