fix: add SQLite database recovery and WAL mode for corruption resilience

- Add scripts/db-recovery.sh for database integrity check and recovery
- Enable WAL mode verification with logging on startup
- Add structured error logging to uptime handlers with monitor context
- Add comprehensive database maintenance documentation

Fixes heartbeat history showing "No History Available" due to database
corruption affecting 6 out of 14 monitors.

backend/internal/database/database_test.go

@@ -5,6 +5,7 @@ import (
 	"testing"
 
 	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
 )
 
 func TestConnect(t *testing.T) {
@@ -27,3 +28,30 @@ func TestConnect_Error(t *testing.T) {
 	_, err := Connect(tempDir)
 	assert.Error(t, err)
 }
+
+func TestConnect_WALMode(t *testing.T) {
+	// Create a file-based database to test WAL mode
+	tempDir := t.TempDir()
+	dbPath := filepath.Join(tempDir, "wal_test.db")
+
+	db, err := Connect(dbPath)
+	require.NoError(t, err)
+	require.NotNil(t, db)
+
+	// Verify WAL mode is enabled
+	var journalMode string
+	err = db.Raw("PRAGMA journal_mode").Scan(&journalMode).Error
+	require.NoError(t, err)
+	assert.Equal(t, "wal", journalMode, "SQLite should be in WAL mode")
+
+	// Verify other PRAGMA settings
+	var busyTimeout int
+	err = db.Raw("PRAGMA busy_timeout").Scan(&busyTimeout).Error
+	require.NoError(t, err)
+	assert.Equal(t, 5000, busyTimeout, "busy_timeout should be 5000ms")
+
+	var synchronous int
+	err = db.Raw("PRAGMA synchronous").Scan(&synchronous).Error
+	require.NoError(t, err)
+	assert.Equal(t, 1, synchronous, "synchronous should be NORMAL (1)")
+}