feat: mcp (#31)

* feat: add mcp connections table and related crud api

* feat: mcp-stdio api

db/queries/mcp.sql

@@ -0,0 +1,30 @@
+-- name: GetMCPConnectionByID :one
+SELECT id, bot_id, name, type, config, is_active, created_at, updated_at
+FROM mcp_connections
+WHERE bot_id = $1 AND id = $2
+LIMIT 1;
+
+-- name: ListMCPConnectionsByBotID :many
+SELECT id, bot_id, name, type, config, is_active, created_at, updated_at
+FROM mcp_connections
+WHERE bot_id = $1
+ORDER BY created_at DESC;
+
+-- name: CreateMCPConnection :one
+INSERT INTO mcp_connections (bot_id, name, type, config, is_active)
+VALUES ($1, $2, $3, $4, $5)
+RETURNING id, bot_id, name, type, config, is_active, created_at, updated_at;
+
+-- name: UpdateMCPConnection :one
+UPDATE mcp_connections
+SET name = $3,
+    type = $4,
+    config = $5,
+    is_active = $6,
+    updated_at = now()
+WHERE bot_id = $1 AND id = $2
+RETURNING id, bot_id, name, type, config, is_active, created_at, updated_at;
+
+-- name: DeleteMCPConnection :exec
+DELETE FROM mcp_connections
+WHERE bot_id = $1 AND id = $2;