fix: update filter_plugin import paths to use keep crate

Co-authored-by: aider (openai/andrew/openrouter/deepseek/deepseek-chat-v3.1) <aider@aider.chat>

src/services/filter_service.rs

@@ -1,4 +1,4 @@
-use crate::filter_plugin::{FilterChain, parse_filter_string};
+use keep::filter_plugin::{FilterChain, parse_filter_string};
 use std::io::Result;
 
 pub struct FilterService;

src/services/item_service.rs

@@ -8,7 +8,7 @@ use crate::services::types::{ItemWithContent, ItemWithMeta};
 use crate::db::{self, Meta};
 use crate::compression_engine::{get_compression_engine, CompressionType};
 use crate::modes::common::settings_compression_type;
-use crate::filter_plugin;
+use keep::filter_plugin;
 use clap::Command;
 use log::debug;
 use rusqlite::Connection;