feat: implement Pocketbook — a Clojure-native synced atom

Offline-first key-value store with atom interface (swap!, deref,
add-watch) that syncs to a SQLite-backed server over Transit.

Server (CLJ):
- SQLite storage with Nippy serialization preserving all Clojure types
- GET /sync?group=G&since=T pull endpoint with prefix-based groups
- POST /sync push endpoint with per-document version checking
- Conflict detection (stale write rejection)
- Token-based auth with per-user group access
- CORS support, soft deletes, purge compaction

Client (CLJS):
- IndexedDB wrapper with Transit serialization
- SyncedAtom implementing IAtom (IDeref, ISwap, IReset, IWatchable)
- Write-through to IndexedDB on every swap!
- Background sync loop (pull + push) with configurable interval
- Online/offline detection with reconnect sync
- Conflict resolution (accept server value)
- ready? channel for initial load
- Custom cache atom support (Reagent ratom compatible)

25 tests, 77 assertions across db, transit, server, and auth.

build.edn

@@ -0,0 +1,5 @@
+{:main       pocketbook.example
+ :output-to  "resources/public/js/main.js"
+ :output-dir "resources/public/js/out"
+ :asset-path "js/out"
+ :optimizations :none}