feat: update default space icon

[AlexAndBear]

Description

• Use processor: ProcessorType.enum.fit when loading previews for space resources in Favorites, Search, Projects, and Trash Overview to avoid cropped thumbnails.
• Normalize the Projects table preview size to 24x24 for consistent table thumbnails.
• Update the default space image asset.

Related Issue

• Fixes <issue_link>

How Has This Been Tested?

• test environment: local development setup (pnpm + Vitest)
• test case 1: pnpm test:unit --run packages/web-pkg/tests/unit/composables/resources/useLoadPreview.spec.ts
• test case 2: pnpm test:unit --run packages/web-app-files/tests/unit/views/Favorites.spec.ts
• test case 3: pnpm test:unit --run packages/web-app-files/tests/unit/components/Search/List.spec.ts
• test case 4: pnpm test:unit --run packages/web-app-files/tests/unit/views/spaces/Projects.spec.ts
• test case 5: pnpm test:unit --run packages/web-app-files/tests/unit/views/trash/Overview.spec.ts
• test case 6: pnpm test:unit --run packages/web-pkg/tests/unit/components/FilesList/ResourceTiles.spec.ts

Types of changes

• Bugfix
• Enhancement (a change that doesn't break existing code or deployments)
• Breaking change (a modification that affects current functionality)
• Technical debt (addressing code that needs refactoring or improvements)
• Tests (adding or improving tests)
• Documentation (updates or additions to documentation)
• Maintenance (like dependency updates or tooling adjustments)