feat(drafts): add bot_drafts schema, automatic table bootstrap, and sync REST endpoints

backend/app/db/init_db.py

@@ -432,3 +432,33 @@ async def ensure_audit_table(engine: AsyncEngine) -> None:
         for stmt in indexes:
             await conn.execute(text(stmt))
     logger.info("audit_log table ensured")
+
+
+async def ensure_bot_drafts_table(engine: AsyncEngine) -> None:
+    """Ensure bot_drafts table and indexes exist for Bale bot quote sync."""
+    ddl = """
+    CREATE TABLE IF NOT EXISTS bot_drafts (
+        id                  UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+        chat_id             BIGINT NOT NULL,
+        kind                VARCHAR(16) NOT NULL,
+        payload             JSONB NOT NULL DEFAULT '{}'::jsonb,
+        missing             JSONB,
+        status              VARCHAR(16) NOT NULL DEFAULT 'active',
+        source              VARCHAR(16),
+        review_message_id   BIGINT,
+        last_bale_update_at TIMESTAMPTZ,
+        created_at          TIMESTAMPTZ NOT NULL DEFAULT now(),
+        updated_at          TIMESTAMPTZ NOT NULL DEFAULT now()
+    )
+    """
+    indexes = (
+        "CREATE INDEX IF NOT EXISTS ix_bot_drafts_chat_id ON bot_drafts(chat_id)",
+        "CREATE INDEX IF NOT EXISTS ix_bot_drafts_chat_status ON bot_drafts(chat_id, status)",
+        "ALTER TABLE bot_drafts ADD COLUMN IF NOT EXISTS last_bale_update_at TIMESTAMPTZ",
+    )
+    async with engine.begin() as conn:
+        await conn.execute(text(ddl))
+        for stmt in indexes:
+            await conn.execute(text(stmt))
+    logger.info("bot_drafts table ensured")
+