docs: comprehensive cleanup and restructuring of project documentation

CODING_STANDARDS.md

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+# TFM aInventory - Coding Standards
+
+**Status**: ACTIVE | **Last Updated**: 2026-04-26
+
+---
+
+## 1. General Principles
+- **Language**: All code, variables, and documentation MUST be in **English**.
+- **Modularity**: Files should be under **300 lines**. Extract logic into hooks (frontend) or services (backend).
+- **Simplicity**: Strict Single Responsibility Principle (SRP). Complexity score < 10.
+
+## 2. Backend (FastAPI / Python)
+- **Framework**: FastAPI (Async/Await)
+- **Validation**: Pydantic v2
+- **Database**: SQLAlchemy 2.0 (Async) + Alembic migrations.
+- **Testing**: Pytest. **Target Coverage: 85%+**.
+- **Naming**: `snake_case` for variables/functions, `PascalCase` for classes.
+
+## 3. Frontend (Next.js / TypeScript)
+- **Framework**: Next.js 15+ (App Router, Strict TypeScript).
+- **Styling**: Tailwind CSS (refer to `DESIGN_SYSTEM.md`).
+- **State Management**: React Hooks + Dexie.js (Offline IndexDB).
+- **Testing**: Vitest for unit, Playwright for E2E. **Target Coverage: 80%+**.
+- **Naming**: `camelCase` for variables/functions, `PascalCase` for components.
+
+## 4. Testing Strategy (MANDATORY)
+- **Test-First**: Write and pass tests BEFORE refactoring or adding features.
+- **Zero Regression**: 100% of existing tests must pass post-change.
+- **Gating**:
+  - Backend: `pytest backend/tests/`
+  - Frontend: `npm run test`
+  - E2E: `npx playwright test`
+
+## 5. Security & Data Integrity
+- **Restricted Actions**: DELETE requires Admin role.
+- **Audit Immortality**: Deleting an item MUST NOT delete its `AuditLog` history.
+- **Authentication**: Never bypassed, even in development. PBKDF2 for local, LDAP for enterprise.
+- **Credentials**: Use `.env` or YAML config. NEVER hardcode or log secrets.
+- **Confirmations**: Destructive actions require triple confirmation or native `window.confirm`.
+
+## 6. Versioning & Workflow
+- **Git**: Use `dev` branch for active work. Never push to `master` directly.
+- **Versioning**: Run `python3 scripts/save_version.py` on every commit.
+- **Documentation**: Every feature change MUST update: `README.md`, `USER_GUIDE.md`, `ARCHITECTURE.md`, `DEPLOYMENT.md`, and `ROADMAP.md`.