feat(db): add wizard_drafts table (V031)

src/GmRelay.Bot/Migrations/V031__add_wizard_drafts.sql

@@ -0,0 +1,21 @@
+-- V031: Per-(chat, thread, owner) wizard drafts for the game-creation wizard (issue #111).
+-- Stores in-progress wizard state in JSONB with a 24h TTL managed by WizardDraftCleanupService.
+
+CREATE TABLE wizard_drafts (
+    id UUID PRIMARY KEY,
+    chat_id BIGINT NOT NULL,
+    message_thread_id INT,
+    owner_telegram_id BIGINT NOT NULL,
+    step TEXT NOT NULL,
+    payload JSONB NOT NULL,
+    draft_message_id BIGINT,
+    created_at TIMESTAMPTZ NOT NULL,
+    updated_at TIMESTAMPTZ NOT NULL,
+    expires_at TIMESTAMPTZ NOT NULL
+);
+
+CREATE INDEX idx_wizard_drafts_owner
+    ON wizard_drafts(chat_id, message_thread_id, owner_telegram_id);
+
+CREATE INDEX idx_wizard_drafts_expires
+    ON wizard_drafts(expires_at);