feat: introduce spec-workflow and upgrade frontend dependencies

This commit introduces the spec-workflow, a set of templates for creating design, product, requirements, and other specification documents. These templates are added to both the root directory and the `apps/frontend` workspace.

Additionally, this commit upgrades the frontend development dependencies for the Astro application. The key changes include:
- Migration from `@astrojs/tailwind` to `@tailwindcss/vite` for Tailwind CSS integration.
- Deletion of the `postcss.config.cjs` file, as it is no longer needed with the new setup.
- Updates to `astro.config.mjs` to use the new Vite plugin for Tailwind CSS.
- General upgrade of Astro and other related dependencies in `apps/frontend/package.json` and the corresponding `pnpm-lock.yaml` file.

.spec-workflow/templates/structure-template.md

@@ -0,0 +1,145 @@
+# Project Structure
+
+## Directory Organization
+
+```
+[Define your project's directory structure. Examples below - adapt to your project type]
+
+Example for a library/package:
+project-root/
+├── src/                    # Source code
+├── tests/                  # Test files  
+├── docs/                   # Documentation
+├── examples/               # Usage examples
+└── [build/dist/out]        # Build output
+
+Example for an application:
+project-root/
+├── [src/app/lib]           # Main source code
+├── [assets/resources]      # Static resources
+├── [config/settings]       # Configuration
+├── [scripts/tools]         # Build/utility scripts
+└── [tests/spec]            # Test files
+
+Common patterns:
+- Group by feature/module
+- Group by layer (UI, business logic, data)
+- Group by type (models, controllers, views)
+- Flat structure for simple projects
+```
+
+## Naming Conventions
+
+### Files
+- **Components/Modules**: [e.g., `PascalCase`, `snake_case`, `kebab-case`]
+- **Services/Handlers**: [e.g., `UserService`, `user_service`, `user-service`]
+- **Utilities/Helpers**: [e.g., `dateUtils`, `date_utils`, `date-utils`]
+- **Tests**: [e.g., `[filename]_test`, `[filename].test`, `[filename]Test`]
+
+### Code
+- **Classes/Types**: [e.g., `PascalCase`, `CamelCase`, `snake_case`]
+- **Functions/Methods**: [e.g., `camelCase`, `snake_case`, `PascalCase`]
+- **Constants**: [e.g., `UPPER_SNAKE_CASE`, `SCREAMING_CASE`, `PascalCase`]
+- **Variables**: [e.g., `camelCase`, `snake_case`, `lowercase`]
+
+## Import Patterns
+
+### Import Order
+1. External dependencies
+2. Internal modules
+3. Relative imports
+4. Style imports
+
+### Module/Package Organization
+```
+[Describe your project's import/include patterns]
+Examples:
+- Absolute imports from project root
+- Relative imports within modules
+- Package/namespace organization
+- Dependency management approach
+```
+
+## Code Structure Patterns
+
+[Define common patterns for organizing code within files. Below are examples - choose what applies to your project]
+
+### Module/Class Organization
+```
+Example patterns:
+1. Imports/includes/dependencies
+2. Constants and configuration
+3. Type/interface definitions
+4. Main implementation
+5. Helper/utility functions
+6. Exports/public API
+```
+
+### Function/Method Organization
+```
+Example patterns:
+- Input validation first
+- Core logic in the middle
+- Error handling throughout
+- Clear return points
+```
+
+### File Organization Principles
+```
+Choose what works for your project:
+- One class/module per file
+- Related functionality grouped together
+- Public API at the top/bottom
+- Implementation details hidden
+```
+
+## Code Organization Principles
+
+1. **Single Responsibility**: Each file should have one clear purpose
+2. **Modularity**: Code should be organized into reusable modules
+3. **Testability**: Structure code to be easily testable
+4. **Consistency**: Follow patterns established in the codebase
+
+## Module Boundaries
+[Define how different parts of your project interact and maintain separation of concerns]
+
+Examples of boundary patterns:
+- **Core vs Plugins**: Core functionality vs extensible plugins
+- **Public API vs Internal**: What's exposed vs implementation details  
+- **Platform-specific vs Cross-platform**: OS-specific code isolation
+- **Stable vs Experimental**: Production code vs experimental features
+- **Dependencies direction**: Which modules can depend on which
+
+## Code Size Guidelines
+[Define your project's guidelines for file and function sizes]
+
+Suggested guidelines:
+- **File size**: [Define maximum lines per file]
+- **Function/Method size**: [Define maximum lines per function]
+- **Class/Module complexity**: [Define complexity limits]
+- **Nesting depth**: [Maximum nesting levels]
+
+## Dashboard/Monitoring Structure (if applicable)
+[How dashboard or monitoring components are organized]
+
+### Example Structure:
+```
+src/
+└── dashboard/          # Self-contained dashboard subsystem
+    ├── server/        # Backend server components
+    ├── client/        # Frontend assets
+    ├── shared/        # Shared types/utilities
+    └── public/        # Static assets
+```
+
+### Separation of Concerns
+- Dashboard isolated from core business logic
+- Own CLI entry point for independent operation
+- Minimal dependencies on main application
+- Can be disabled without affecting core functionality
+
+## Documentation Standards
+- All public APIs must have documentation
+- Complex logic should include inline comments
+- README files for major modules
+- Follow language-specific documentation conventions