Add mobile app support and opening training feature

This commit implements iOS/Android mobile app support using Capacitor
and adds a comprehensive opening training feature with LLM-powered
explanations.

## Mobile App Infrastructure

- Add Capacitor configuration for iOS/Android builds
- Create mobile build script that excludes API routes
- Update Next.js config for conditional static export
- Add layout components with generateStaticParams for static builds
- Generate 500+ static pages for offline mobile use

## Chess Engine Abstraction

- Create ChessEngine interface for pluggable implementations
- Add LocalEngine (GPL - uses stockfish.js in browser)
- Add RemoteEngine (proprietary - calls API server)
- Factory pattern selects engine based on environment
- Enables GPL compliance for web, proprietary for mobile

## Opening Training Feature

- Interactive opening repertoire training
- Move validation with engine-backed feedback
- LLM explanations using Gemini API
- Wikipedia integration for opening context
- Opening family grouping (e4, d4, c4, etc.)
- Session state management
- Real-time move feedback with evaluation

Components:
- OpeningSelector: Browse and select openings by family
- OpeningTrainer: Main training interface with chessboard
- MoveFeedback: Display move quality and LLM explanations
- WikipediaSummary: Show opening history and context
- ErrorBoundary: Graceful error handling

Services:
- openingLoader: Load and filter opening database
- engineService: Engine evaluation wrapper
- moveValidator: Validate moves against repertoire
- feedbackGenerator: Generate contextual feedback
- wikipediaService: Fetch and cache Wikipedia data
- sessionManager: Track training session state

## Wikipedia Integration

- Automatic Wikipedia article fetching for openings
- Client-side and server-side caching
- Sanitized summaries with proper formatting
- Link opening database to Wikipedia slugs
- API endpoints for on-demand fetching

## Docker Improvements

- Add entrypoint script for automatic data setup
- Fetch Wikipedia data on first container startup
- Generate opening move index automatically
- Remove generated data from git (public/openings/*.json, public/wikipedia/*.json)
- Add READMEs explaining data requirements
- Update .gitignore for generated files

## Dual Licensing Strategy

- Add LICENSING.md explaining dual licensing approach
- GPL-3.0 for web builds (includes Stockfish)
- Proprietary option for mobile builds (no GPL code)
- Single codebase, multiple licensing models
- Legal compliance documented

## API Endpoints

- POST /api/v1/llm/opening-explanation - Get LLM move explanations
- GET /api/v1/wikipedia/summary - Fetch Wikipedia summaries

## Type Updates

- Add openingTraining types
- Update Tutor component to use ChessEngine interface
- Add Gemini error handling types

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

public/wikipedia/README.md

@@ -0,0 +1,53 @@
+# Wikipedia Opening Cache
+
+This directory contains cached Wikipedia article summaries for chess openings.
+
+## What is this?
+
+The Wikipedia cache provides educational context about chess openings:
+- Article summaries
+- Opening history
+- Strategic ideas
+- Notable games
+
+## Automatic Setup (Docker)
+
+When running via Docker, Wikipedia data is **automatically fetched** on first startup:
+
+```bash
+docker-compose up
+# Will fetch Wikipedia data on first run
+# Cached for subsequent runs
+```
+
+The Docker entrypoint script (`scripts/docker-entrypoint.sh`) handles:
+1. Fetching Wikipedia articles for all openings
+2. Sanitizing/formatting the data
+3. Linking Wikipedia slugs to opening database
+
+## Manual Setup (Development)
+
+```bash
+# Fetch Wikipedia articles
+npm run cache:wikipedia
+
+# Update opening database with Wikipedia slugs
+npm run update:wikipedia-slugs
+```
+
+## Cache Invalidation
+
+To refresh Wikipedia data:
+
+```bash
+rm public/wikipedia/*.json
+docker-compose restart
+# Or: npm run cache:wikipedia
+```
+
+## Notes
+
+- Files are **not committed to git** (generated at runtime)
+- Wikipedia API has rate limits (be patient)
+- Wikipedia content is optional (app works without it)
+- `.initialized` marker prevents re-fetching on every startup