Fix DB lock error: clear message + instructions, fix passphrase reprompt

Storage:
- Detects sled lock contention, shows actionable error:
  "Database locked by another warzone process"
  with ps command to find the process and rm command to force unlock

TUI:
- Poll loop no longer calls load_seed() (was re-prompting passphrase)
- Seed passed from main.rs to run_tui to poll_loop
- Single passphrase prompt per app launch

Warnings fixed:
- Removed unused `Context` import in tui/app.rs
- Added #[allow(dead_code)] on validate_token (used when auth middleware wired)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

warzone/crates/warzone-client/src/tui/app.rs

@@ -1,7 +1,7 @@
 use std::sync::{Arc, Mutex};
 use std::time::Duration;
 
-use anyhow::{Context, Result};
+use anyhow::Result;
 use crossterm::event::{self, Event, KeyCode, KeyModifiers};
 use ratatui::layout::{Constraint, Direction, Layout};
 use ratatui::style::{Color, Modifier, Style};
@@ -741,6 +741,7 @@ pub async fn run_tui(
     peer_fp: Option<String>,
     server_url: String,
     identity: IdentityKeyPair,
+    poll_seed: warzone_protocol::identity::Seed,
     db: LocalDb,
 ) -> Result<()> {
     let mut terminal = ratatui::init();
@@ -749,9 +750,8 @@ pub async fn run_tui(
 
     let mut app = App::new(our_fp.clone(), peer_fp, server_url);
 
-    // Spawn background poll task
-    // We need a second IdentityKeyPair for the poll loop — re-derive from seed
-    let poll_identity = crate::keystore::load_seed()?.derive_identity();
+    // Derive a second identity for the poll loop (can't clone IdentityKeyPair)
+    let poll_identity = poll_seed.derive_identity();
     let poll_messages = app.messages.clone();
     let poll_client = client.clone();
     let poll_db = db.clone();