docs: add CLAUDE.md and project documentation

Add CLAUDE.md for AI assistant context. Create four new docs:
deployment-guide.md (full deploy flow + secret rotation + rollback),
code-standards.md (formatting, naming, module conventions, testing),
codebase-summary.md (tech stack, modules, data flows, external APIs),
development-roadmap.md (completed phases + planned work).

docs/codebase-summary.md

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+# Codebase Summary
+
+## Overview
+
+Telegram bot on Cloudflare Workers with a plug-n-play module system. grammY handles Telegram API; modules register commands with three visibility levels. Data stored in Cloudflare KV behind a prefixed `KVStore` interface.
+
+## Tech Stack
+
+| Layer | Technology |
+|-------|-----------|
+| Runtime | Cloudflare Workers (V8 isolates) |
+| Bot framework | grammY 1.x |
+| Storage | Cloudflare KV |
+| Linter/Formatter | Biome |
+| Tests | Vitest |
+| Deploy | Wrangler CLI |
+
+## Active Modules
+
+| Module | Status | Commands | Description |
+|--------|--------|----------|-------------|
+| `util` | Complete | `/info`, `/help` | Bot info and command help renderer |
+| `trading` | Complete | `/trade_topup`, `/trade_buy`, `/trade_sell`, `/trade_convert`, `/trade_stats` | Paper trading with crypto, VN stocks, forex, gold |
+| `misc` | Stub | `/ping`, `/mstats`, `/fortytwo` | Health check + DB demo |
+| `wordle` | Stub | `/wordle`, `/wstats`, `/konami` | Placeholder for word game |
+| `loldle` | Stub | `/loldle`, `/ggwp` | Placeholder for LoL game |
+
+## Key Data Flows
+
+### Command Processing
+```
+Telegram update → POST /webhook → grammY secret validation
+→ getBot(env) → dispatcher routes /cmd → module handler
+→ handler reads/writes KV via db.getJSON/putJSON
+→ ctx.reply() → response to Telegram
+```
+
+### Trading Module Price Fetch
+```
+User sends /trade_buy → handler calls getPrice(db, symbol)
+→ getPrices(db) checks KV cache (key: "prices:latest")
+→ if stale (>60s): fetch CoinGecko + TCBS + ER-API in parallel
+→ merge results, cache in KV → return price in VND
+```
+
+### Deploy Pipeline
+```
+npm run deploy → wrangler deploy (upload to CF)
+→ scripts/register.js → buildRegistry with stub KV
+→ POST setWebhook + POST setMyCommands to Telegram API
+```
+
+## External Dependencies
+
+| Dependency | Purpose | Version |
+|-----------|---------|---------|
+| `grammy` | Telegram Bot API framework | ^1.30.0 |
+| `@biomejs/biome` | Linting + formatting (dev) | ^1.9.0 |
+| `vitest` | Test runner (dev) | ^2.1.0 |
+| `wrangler` | Cloudflare Workers CLI (dev) | ^3.90.0 |
+
+## External APIs (Trading Module)
+
+| API | Purpose | Auth | Rate Limit |
+|-----|---------|------|-----------|
+| CoinGecko `/api/v3/simple/price` | Crypto + gold prices in VND | None | 30 calls/min (free) |
+| TCBS `/stock-insight/v1/stock/bars-long-term` | Vietnam stock close prices | None | Unofficial |
+| open.er-api.com `/v6/latest/USD` | USD/VND forex rate | None | 1,500/month (free) |
+
+## Test Coverage
+
+110 tests across 11 test files:
+
+| Area | Tests | What's Covered |
+|------|-------|---------------|
+| DB layer | 19 | KV store, prefixing, JSON helpers, pagination |
+| Module framework | 33 | Registry, dispatcher, validators, help renderer |
+| Utilities | 4 | HTML escaping |
+| Trading module | 54 | Symbols, formatters, portfolio CRUD, all 5 command handlers |