fix(ui): keep OIDC query params as strings to fix invalid_value error

[Summpot]

Why

When the Minecraft mod redirects the browser to /login?oidc=1&..., the login page fails with a zod validation error:

{ "code": "invalid_value", "values": ["1"], "path": ["oidc"], "message": "Invalid input" }

The root cause is in the frontend, not the backend. TanStack Router's default parseSearch (built on JSON.parse) coerces query-string values into booleans/numbers, so oidc=1 arrives as the number 1. The oidcSearchSchema expects a string literal via z.literal('1'), so validation fails and the login page cannot render the OIDC flow.

Approach

Configure the router in src/router.tsx with a string-preserving parseSearch/stringifySearch. This keeps every query value as a raw string, so z.literal('1') validates correctly and the isOidcFlow (params.oidc === '1') check works again.

The stringify parser deliberately throws for plain strings so they are encoded raw; only structured values (arrays/objects) are JSON-stringified by the helper wrapper.

Notes

• Verified against zod v4 (invalid_value reproduces exactly when a number 1 is passed to z.literal('1')) and verified the string-preserving parser round-trips correctly for oidc=1, URL-encoded redirect URIs, and spaced state values.
• Other routes using search params (profile) also expect string values, so the string-preserving behavior is safe and consistent.