Clean: eliminate all compilation warnings

- Remove unused imports (regex::Regex, OnceLock)
- Remove unused static FILE_EXTENSIONS
- Prefix unused variable with underscore
- Suppress deprecated warnings from generic-array

Code now compiles without warnings!

src/analysis/entities.rs

@@ -1,9 +1,6 @@
 /// Entity extraction from window titles and process names
 use super::Entities;
-use regex::Regex;
-use std::sync::OnceLock;
 
-static FILE_EXTENSIONS: OnceLock<Regex> = OnceLock::new();
 static PROGRAMMING_LANGUAGES: &[(&str, &[&str])] = &[
     ("Rust", &[".rs", "rust", "cargo"]),
     ("Python", &[".py", "python", "pip", "pytest"]),

src/main.rs

@@ -264,7 +264,7 @@ fn cleanup_data(config: &config::Config, password: &str, retention_days: i64) ->
     info!("Cleaning up data older than {} days...", retention_days);
 
     let mut db = storage::Database::new(&config.storage.db_path, password)?;
-    let deleted = db.cleanup_old_data(retention_days)?;
+    let _deleted = db.cleanup_old_data(retention_days)?;
 
     info!("Cleanup completed");
     println!("Data older than {} days has been removed", retention_days);

src/storage/encryption.rs

@@ -1,3 +1,4 @@
+#![allow(deprecated)]
 /// Encryption utilities using AES-256-GCM with PBKDF2 key derivation
 use aes_gcm::{
     aead::{Aead, KeyInit, OsRng},