# Implementation Plan: [FEATURE]

**Branch**: `[###-feature-name]` | **Date**: [DATE] | **Spec**: [link]
**Input**: Feature specification from `/specs/[###-feature-name]/spec.md`

**Note**: This template is filled in by the `/speckit.plan` command. See `.specify/templates/commands/plan.md` for the execution workflow.

## Summary

Unify frontend styling using a centralized Tailwind CSS configuration and a set of standardized Svelte wrapper components. Implement internationalization (i18n) with support for Russian (default) and English, persisting language preference in LocalStorage.

## Technical Context

**Language/Version**: Node.js 18+ (Frontend Build), Svelte 5.x
**Primary Dependencies**: SvelteKit, Tailwind CSS, `date-fns` (existing)
**Storage**: LocalStorage (for language preference)
**Testing**: Manual verification per User Scenarios (Visual Regression)
**Target Platform**: Web Browser (Responsive)
**Project Type**: Web application (Frontend)
**Performance Goals**: Instant language switching, zero layout shift
**Constraints**: Must support existing pages without breaking layout
**Scale/Scope**: ~10-15 core UI components, global CSS update

## Constitution Check

*GATE: Must pass before Phase 0 research. Re-check after Phase 1 design.*

- **Semantic Protocol Compliance**: PASS. New Svelte components must follow the Component Header standard.
- **Causal Validity**: PASS. Design System (Tokens) and Component Contracts will be defined before implementation.
- **Immutability of Architecture**: PASS. No changes to backend architecture; strictly frontend presentation layer.
- **Design by Contract**: PASS. Components will define strict props/interfaces.
- **Everything is a Plugin**: N/A. UI components are not backend plugins, but will be modular.

## Project Structure

### Documentation (this feature)

```text
specs/[###-feature]/
├── plan.md              # This file (/speckit.plan command output)
├── research.md          # Phase 0 output (/speckit.plan command)
├── data-model.md        # Phase 1 output (/speckit.plan command)
├── quickstart.md        # Phase 1 output (/speckit.plan command)
├── contracts/           # Phase 1 output (/speckit.plan command)
└── tasks.md             # Phase 2 output (/speckit.tasks command - NOT created by /speckit.plan)
```

### Source Code (repository root)

```text
frontend/
├── src/
│   ├── lib/
│   │   ├── i18n/              # [NEW] Translation dictionaries and stores
│   │   └── ui/                # [NEW] Standardized Svelte components
│   ├── components/            # [EXISTING] To be refactored to use lib/ui
│   ├── routes/                # [EXISTING] Pages
│   └── app.css                # [EXISTING] Global styles (Tailwind directives)
```

**Structure Decision**: Adopting a standard SvelteKit structure where reusable UI components and logic (i18n) reside in `src/lib`, accessible via `$lib` alias. Existing `components` directory will be gradually refactored or moved to `lib/ui` if generic enough.

## Complexity Tracking

> **Fill ONLY if Constitution Check has violations that must be justified**

| Violation | Why Needed | Simpler Alternative Rejected Because |
|-----------|------------|-------------------------------------|
| [e.g., 4th project] | [current need] | [why 3 projects insufficient] |
| [e.g., Repository pattern] | [specific problem] | [why direct DB access insufficient] |