Implement local SQLite index database with repositories

- Add SQLite database connection management with proper error handling
- Implement schema for files, chunks, blobs, and snapshots tables
- Create repository pattern for each database table
- Add transaction support with proper rollback handling
- Integrate database module with fx dependency injection
- Make index path configurable via VAULTIK_INDEX_PATH env var
- Add fatal error handling for database integrity issues
- Update DESIGN.md to clarify file_chunks vs chunk_files distinction
- Remove FinalHash from BlobInfo (blobs are content-addressable)
- Add file metadata support (mtime, ctime, mode, uid, gid, symlinks)

internal/database/snapshots.go

@@ -0,0 +1,131 @@
+package database
+
+import (
+	"context"
+	"database/sql"
+	"fmt"
+	"time"
+)
+
+type SnapshotRepository struct {
+	db *DB
+}
+
+func NewSnapshotRepository(db *DB) *SnapshotRepository {
+	return &SnapshotRepository{db: db}
+}
+
+func (r *SnapshotRepository) Create(ctx context.Context, tx *sql.Tx, snapshot *Snapshot) error {
+	query := `
+		INSERT INTO snapshots (id, hostname, vaultik_version, created_ts, file_count, chunk_count, blob_count)
+		VALUES (?, ?, ?, ?, ?, ?, ?)
+	`
+
+	var err error
+	if tx != nil {
+		_, err = tx.ExecContext(ctx, query, snapshot.ID, snapshot.Hostname, snapshot.VaultikVersion, snapshot.CreatedTS.Unix(), snapshot.FileCount, snapshot.ChunkCount, snapshot.BlobCount)
+	} else {
+		_, err = r.db.conn.ExecContext(ctx, query, snapshot.ID, snapshot.Hostname, snapshot.VaultikVersion, snapshot.CreatedTS.Unix(), snapshot.FileCount, snapshot.ChunkCount, snapshot.BlobCount)
+	}
+
+	if err != nil {
+		return fmt.Errorf("inserting snapshot: %w", err)
+	}
+
+	return nil
+}
+
+func (r *SnapshotRepository) UpdateCounts(ctx context.Context, tx *sql.Tx, snapshotID string, fileCount, chunkCount, blobCount int64) error {
+	query := `
+		UPDATE snapshots 
+		SET file_count = ?,
+		    chunk_count = ?,
+		    blob_count = ?
+		WHERE id = ?
+	`
+
+	var err error
+	if tx != nil {
+		_, err = tx.ExecContext(ctx, query, fileCount, chunkCount, blobCount, snapshotID)
+	} else {
+		_, err = r.db.conn.ExecContext(ctx, query, fileCount, chunkCount, blobCount, snapshotID)
+	}
+
+	if err != nil {
+		return fmt.Errorf("updating snapshot: %w", err)
+	}
+
+	return nil
+}
+
+func (r *SnapshotRepository) GetByID(ctx context.Context, snapshotID string) (*Snapshot, error) {
+	query := `
+		SELECT id, hostname, vaultik_version, created_ts, file_count, chunk_count, blob_count
+		FROM snapshots
+		WHERE id = ?
+	`
+
+	var snapshot Snapshot
+	var createdTSUnix int64
+
+	err := r.db.conn.QueryRowContext(ctx, query, snapshotID).Scan(
+		&snapshot.ID,
+		&snapshot.Hostname,
+		&snapshot.VaultikVersion,
+		&createdTSUnix,
+		&snapshot.FileCount,
+		&snapshot.ChunkCount,
+		&snapshot.BlobCount,
+	)
+
+	if err == sql.ErrNoRows {
+		return nil, nil
+	}
+	if err != nil {
+		return nil, fmt.Errorf("querying snapshot: %w", err)
+	}
+
+	snapshot.CreatedTS = time.Unix(createdTSUnix, 0)
+
+	return &snapshot, nil
+}
+
+func (r *SnapshotRepository) ListRecent(ctx context.Context, limit int) ([]*Snapshot, error) {
+	query := `
+		SELECT id, hostname, vaultik_version, created_ts, file_count, chunk_count, blob_count
+		FROM snapshots
+		ORDER BY created_ts DESC
+		LIMIT ?
+	`
+
+	rows, err := r.db.conn.QueryContext(ctx, query, limit)
+	if err != nil {
+		return nil, fmt.Errorf("querying snapshots: %w", err)
+	}
+	defer CloseRows(rows)
+
+	var snapshots []*Snapshot
+	for rows.Next() {
+		var snapshot Snapshot
+		var createdTSUnix int64
+
+		err := rows.Scan(
+			&snapshot.ID,
+			&snapshot.Hostname,
+			&snapshot.VaultikVersion,
+			&createdTSUnix,
+			&snapshot.FileCount,
+			&snapshot.ChunkCount,
+			&snapshot.BlobCount,
+		)
+		if err != nil {
+			return nil, fmt.Errorf("scanning snapshot: %w", err)
+		}
+
+		snapshot.CreatedTS = time.Unix(createdTSUnix, 0)
+
+		snapshots = append(snapshots, &snapshot)
+	}
+
+	return snapshots, rows.Err()
+}