feat: Codex integration

fix: add bootstrap step

refactor(app): replace monolithic engine/io with session + history + blobs

feat: google fonts

feat: pluggable engine system with DAG pipeline

refactor: simplify Tauri setup and dev server

refactor: rewrite backend storage, config, and runtime

feat: bootstrap window

refactor: merge crates

chore: rename koharu-app to koharu

perf: download with http range

feat: add tracing events for download events

Revert "refactor: renmae koharu-app to koharu"

refactor: renmae koharu-app to koharu

feat: Implement core application structure and functionality