chore: Upload production source maps to Sentry

[do0ori]

Why

A RangeError: Maximum call stack size exceeded came in from production (issue 7738519042) with a fully minified stack — alternating Ok / Qk frames. Determining whether it was ours required diffing the reported line numbers against the deployed bundle by hand:

Sentry frame	Reality
/visual-timer/:226:382 (Qk)	index.html is 61 lines
/visual-timer/:226:63 (Ok)	index-BJf-jupJ.js is 214 lines
/visual-timer/:190:70	bundle line 190 is 23 chars long

Every frame was attributed to the document URL, and index.html carries no inline script — so the recursion came from a script injected into the page (iOS Chrome extension / in-app injection) and was picked up by the global onerror handler. That should have taken seconds to establish, not a manual bundle diff.

What

• Add @sentry/vite-plugin. Source maps are generated (hidden) only when SENTRY_AUTH_TOKEN is present, uploaded, then deleted from dist — so they are never published to GitHub Pages and local builds skip them entirely.
• Pass SENTRY_AUTH_TOKEN to the build step; org and project are plain constants in vite.config.ts.
• Set release on Sentry.init so uploaded maps match incoming events.
• Tag events with own_code, derived from whether any located frame belongs to our hashed bundle under assets/. Events with no located frames default to true so nothing real is mislabelled.

Verification

• npm run build passes; dist contains no .map files.
• npm test — 32/32 passing.
• End-to-end upload is only exercisable once this lands on main; the plugin is a no-op without the token, so a failure there cannot break the deploy.

Note

Unrelated to this crash, src/hooks/useTimer.ts:221 calls start(false) during render, which triggers setState and a fetch in the render phase. Worth a separate fix.

🤖 Generated with Claude Code

https://claude.ai/code/session_01MUBfrDZLkPRPZQJxJWzeU4