feat: add frontend development guidelines and structure documentation

- Introduced API guidelines for interface contracts and request handling.
- Added design tokens usage guidelines for consistent styling across the project.
- Established DTO guidelines for defining request parameters and response data types.
- Created frontend structure guidelines to clarify directory organization and code placement rules.
- Compiled a comprehensive frontend development guideline document covering various aspects of the development process.
- Implemented quality guidelines to ensure code maintainability and adherence to best practices.

AI-RD-Workflow/20-skills/pm-requirement-refine/SKILL.md

@@ -0,0 +1,39 @@
+---
+name: pm-requirement-refine
+description: Refine user-facing requirements from a PM perspective. Use when Codex needs to transform reviewed intake into traceable user requirement, requirement analysis, scenario analysis, user stories, acceptance criteria, and open questions.
+---
+
+# PM Requirement Refine
+
+Refine a reviewed intake into PM-side requirement artifacts.
+
+## Inputs
+
+- INTAKE.
+- PM review note.
+- Existing business context.
+
+## Process
+
+1. Write the user requirement in user-goal language.
+2. Extract business value, target users, constraints, and non-goals.
+3. Produce requirement analysis with assumptions, dependencies, and risks.
+4. Produce scenario analysis for main, alternative, exception, and boundary scenarios.
+5. Define acceptance criteria that can be verified later.
+6. Create traceability metadata for all generated artifacts.
+
+## Output
+
+Generate or update:
+
+- UR.
+- RA.
+- SA.
+- Open question list.
+
+## Quality Bar
+
+- Each requirement has a clear user or business value.
+- Each scenario maps to at least one requirement.
+- Each acceptance criterion is observable.
+- Unknowns are not hidden inside polished prose.