feat: doc editor + offline mode + stats trio + i18n framework

feat(tools): 3 new tools - Jina Reader URL fetch + YouTube transcript + SQL/CSV analysis

fix(mistral): use official @ai-sdk/mistral provider for tool calling

feat(composer): default AI toggles ON + toast feedback on click

feat(message): KaTeX math rendering via remark-math + rehype-katex

feat(cloud-sync): GitHub OAuth + Upstash Redis cross-device sync (LWW)

feat(phase1-wave3): pin/tags/FTS + file upload + personas + memory

feat(phase1): theme toggle + slash commands + continue button + 4 new tools

chore: regenerate package-lock.json to fix CI

feat(ui): premium redesign inspired by shadcn AI Elements

feat: rebuild UI with Next.js 15 + shadcn/ui + Vercel AI SDK