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/se-requirement-analysis/SKILL.md

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+---
+name: se-requirement-analysis
+description: Create engineering-side objective requirements and development requirements from PM-side artifacts. Use when Codex needs to transform UR, requirement analysis, and scenario analysis into OR and DR with traceable functional, non-functional, interface, data, dependency, and risk requirements.
+---
+
+# SE Requirement Analysis
+
+Transform PM artifacts into engineering requirements.
+
+## Inputs
+
+- UR.
+- RA.
+- SA.
+- SE review note.
+
+## Process
+
+1. Create OR with engineering objective, delivery scope, success metrics, and constraints.
+2. Create DR with functional requirements, non-functional requirements, API/interface requirements, data requirements, dependencies, compatibility, rollout, and observability.
+3. Map each OR/DR item back to source IDs.
+4. Mark open questions and assumptions.
+5. Identify DS candidates for RD breakdown.
+
+## Output
+
+Generate:
+
+- OR.
+- DR.
+- Traceability updates.
+
+## Quality Bar
+
+- Every critical UR has engineering coverage or an explicit exclusion.
+- DR items are specific enough for detailed design.
+- Risks and unknowns are visible.