Add exclude patterns, snapshot prune, and other improvements

- Implement exclude patterns with anchored pattern support:
  - Patterns starting with / only match from root of source dir
  - Unanchored patterns match anywhere in path
  - Support for glob patterns (*.log, .*, **/*.pack)
  - Directory patterns skip entire subtrees
  - Add gobwas/glob dependency for pattern matching
  - Add 16 comprehensive tests for exclude functionality

- Add snapshot prune command to clean orphaned data:
  - Removes incomplete snapshots from database
  - Cleans orphaned files, chunks, and blobs
  - Runs automatically at backup start for consistency

- Add snapshot remove command for deleting snapshots

- Add VAULTIK_AGE_SECRET_KEY environment variable support

- Fix duplicate fx module provider in restore command

- Change snapshot ID format to hostname_YYYY-MM-DDTHH:MM:SSZ

internal/database/files.go

@@ -302,6 +302,55 @@ func (r *FileRepository) ListByPrefix(ctx context.Context, prefix string) ([]*Fi
 	return files, rows.Err()
 }
 
+// CreateBatch inserts or updates multiple files in a single statement for efficiency.
+// File IDs must be pre-generated before calling this method.
+func (r *FileRepository) CreateBatch(ctx context.Context, tx *sql.Tx, files []*File) error {
+	if len(files) == 0 {
+		return nil
+	}
+
+	// Each File has 9 values, so batch at 100 to be safe with SQLite's variable limit
+	const batchSize = 100
+
+	for i := 0; i < len(files); i += batchSize {
+		end := i + batchSize
+		if end > len(files) {
+			end = len(files)
+		}
+		batch := files[i:end]
+
+		query := `INSERT INTO files (id, path, mtime, ctime, size, mode, uid, gid, link_target) VALUES `
+		args := make([]interface{}, 0, len(batch)*9)
+		for j, f := range batch {
+			if j > 0 {
+				query += ", "
+			}
+			query += "(?, ?, ?, ?, ?, ?, ?, ?, ?)"
+			args = append(args, f.ID, f.Path, f.MTime.Unix(), f.CTime.Unix(), f.Size, f.Mode, f.UID, f.GID, f.LinkTarget)
+		}
+		query += ` ON CONFLICT(path) DO UPDATE SET
+			mtime = excluded.mtime,
+			ctime = excluded.ctime,
+			size = excluded.size,
+			mode = excluded.mode,
+			uid = excluded.uid,
+			gid = excluded.gid,
+			link_target = excluded.link_target`
+
+		var err error
+		if tx != nil {
+			_, err = tx.ExecContext(ctx, query, args...)
+		} else {
+			_, err = r.db.ExecWithLog(ctx, query, args...)
+		}
+		if err != nil {
+			return fmt.Errorf("batch inserting files: %w", err)
+		}
+	}
+
+	return nil
+}
+
 // DeleteOrphaned deletes files that are not referenced by any snapshot
 func (r *FileRepository) DeleteOrphaned(ctx context.Context) error {
 	query := `