Add last modified tracking: show 'Last modified: date by username' in document viewer

- Added modified_by column to files table
- Updated WOPI PutFile to track who modified the file
- Updated view handlers to return file metadata (name, size, lastModified, modifiedByName)
- Updated Flutter models and UI to display last modified info

go_cloud/internal/database/db.go

@@ -126,15 +126,17 @@ type Activity struct {
 }
 
 type File struct {
-	ID           uuid.UUID
-	OrgID        *uuid.UUID
-	UserID       *uuid.UUID
-	Name         string
-	Path         string
-	Type         string
-	Size         int64
-	LastModified time.Time
-	CreatedAt    time.Time
+	ID             uuid.UUID
+	OrgID          *uuid.UUID
+	UserID         *uuid.UUID
+	Name           string
+	Path           string
+	Type           string
+	Size           int64
+	LastModified   time.Time
+	CreatedAt      time.Time
+	ModifiedBy     *uuid.UUID
+	ModifiedByName string
 }
 
 func (db *DB) GetOrCreateUser(ctx context.Context, sub, email, name string) (*User, error) {
@@ -465,12 +467,17 @@ func (db *DB) GetFileByID(ctx context.Context, fileID uuid.UUID) (*File, error)
 	var f File
 	var orgNull sql.NullString
 	var userNull sql.NullString
+	var modifiedByNull sql.NullString
+	var modifiedByNameNull sql.NullString
 
 	err := db.QueryRowContext(ctx, `
-		SELECT id, org_id::text, user_id::text, name, path, type, size, last_modified, created_at
-		FROM files
-		WHERE id = $1
-	`, fileID).Scan(&f.ID, &orgNull, &userNull, &f.Name, &f.Path, &f.Type, &f.Size, &f.LastModified, &f.CreatedAt)
+		SELECT f.id, f.org_id::text, f.user_id::text, f.name, f.path, f.type, f.size, f.last_modified, f.created_at,
+		       f.modified_by::text, u.display_name
+		FROM files f
+		LEFT JOIN users u ON f.modified_by = u.id
+		WHERE f.id = $1
+	`, fileID).Scan(&f.ID, &orgNull, &userNull, &f.Name, &f.Path, &f.Type, &f.Size, &f.LastModified, &f.CreatedAt,
+		&modifiedByNull, &modifiedByNameNull)
 
 	if err != nil {
 		return nil, err
@@ -484,17 +491,24 @@ func (db *DB) GetFileByID(ctx context.Context, fileID uuid.UUID) (*File, error)
 		uid, _ := uuid.Parse(userNull.String)
 		f.UserID = &uid
 	}
+	if modifiedByNull.Valid {
+		mid, _ := uuid.Parse(modifiedByNull.String)
+		f.ModifiedBy = &mid
+	}
+	if modifiedByNameNull.Valid {
+		f.ModifiedByName = modifiedByNameNull.String
+	}
 
 	return &f, nil
 }
 
-// UpdateFileSize updates the size and modification time of a file
-func (db *DB) UpdateFileSize(ctx context.Context, fileID uuid.UUID, size int64) error {
+// UpdateFileSize updates the size, modification time, and modifier of a file
+func (db *DB) UpdateFileSize(ctx context.Context, fileID uuid.UUID, size int64, modifiedBy *uuid.UUID) error {
 	_, err := db.ExecContext(ctx, `
 		UPDATE files
-		SET size = $1, last_modified = NOW()
+		SET size = $1, last_modified = NOW(), modified_by = $3
 		WHERE id = $2
-	`, size, fileID)
+	`, size, fileID, modifiedBy)
 	return err
 }