Switch to incremental vacuum for non-blocking space reclamation

- Use PRAGMA incremental_vacuum instead of full VACUUM
- Frees ~1000 pages (~4MB) per run without blocking writes
- Run every 10 minutes instead of 6 hours since it's lightweight
- Set auto_vacuum=INCREMENTAL pragma for new databases
- Remove blocking VACUUM on startup

internal/database/database.go

@@ -113,6 +113,7 @@ func (d *Database) Initialize() error {
 		"PRAGMA wal_checkpoint(TRUNCATE)", // Checkpoint and truncate WAL now
 		"PRAGMA busy_timeout=5000",        // 5 second busy timeout
 		"PRAGMA analysis_limit=0",         // Disable automatic ANALYZE
+		"PRAGMA auto_vacuum=INCREMENTAL",  // Enable incremental vacuum (new DBs only)
 	}
 
 	for _, pragma := range pragmas {
@@ -126,12 +127,6 @@ func (d *Database) Initialize() error {
 		return err
 	}
 
-	// Run VACUUM on startup to optimize database
-	d.logger.Info("Running VACUUM to optimize database (this may take a moment)")
-	if err := d.exec("VACUUM"); err != nil {
-		d.logger.Warn("Failed to VACUUM database", "error", err)
-	}
-
 	return nil
 }
 
@@ -1951,11 +1946,15 @@ func (d *Database) getIPv6Info(ctx context.Context, ip string, parsedIP net.IP)
 	return info, nil
 }
 
-// Vacuum runs the SQLite VACUUM command to reclaim unused space and defragment the database.
+// Vacuum runs incremental vacuum to reclaim unused pages without blocking writes.
+// It frees up to the specified number of pages per call (0 = all freeable pages).
 func (d *Database) Vacuum(ctx context.Context) error {
-	_, err := d.db.ExecContext(ctx, "VACUUM")
+	// Free up to 1000 pages per call (~4MB with default 4KB page size)
+	// This keeps each vacuum operation quick and non-blocking
+	const pagesToFree = 1000
+	_, err := d.db.ExecContext(ctx, fmt.Sprintf("PRAGMA incremental_vacuum(%d)", pagesToFree))
 	if err != nil {
-		return fmt.Errorf("failed to vacuum database: %w", err)
+		return fmt.Errorf("failed to run incremental vacuum: %w", err)
 	}
 
 	return nil