types: restore Supabase row typing, fix parseInput inference (586→76 tsc errors)

The installed supabase-js (2.99, 5 generics) is incompatible with
@supabase/ssr@0.6.1 (calls it with 3), collapsing the server client's
schema to `never` — the root cause of ~450 of the 586 hidden type errors
(next.config typescript.ignoreBuildErrors masks them all).

- lib/supabase/server.ts: annotate the factory as SupabaseClient<Database>
  and bridge the ssr/js impedance mismatch at the one documented boundary;
  type the setAll cookie params.
- lib/supabase/proxy.ts, proxy.ts: type the setAll cookie params.
- lib/auth-helpers.ts: parseInput now infers its result from the schema via
  z.infer (was a fragile ZodSchema<T> that widened outputs to {}).
- lib/validations.ts: annotate flexibleDateTime's output type.
- types/database.ts: add class_signup_tx / class_cancel_tx RPC signatures
  (called but absent; pending full regeneration).
- tsconfig.json: target ES2020 (door-log-logic uses BigInt literals).
- vitest.setup.ts: import beforeAll/afterAll instead of relying on globals.

No runtime behavior change; 639 tests still green. ignoreBuildErrors stays
on until the remaining errors reach zero.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

proxy.ts

@@ -1,7 +1,10 @@
 import { updateSession } from '@/lib/supabase/proxy'
-import { createServerClient } from '@supabase/ssr'
+import { createServerClient, type CookieOptions } from '@supabase/ssr'
 import { NextResponse, type NextRequest } from 'next/server'
 
+/** Shape `@supabase/ssr` passes to `setAll` (typing lost to the ssr/js version drift). */
+type CookiesToSet = { name: string; value: string; options: CookieOptions }[]
+
 // Public routes are reachable without an authenticated session. The
 // /resources subsite is the legacy hackerspace.sh content baked in; the
 // five individual resource routes (/zine, /governance, /space-after-dark,
@@ -77,7 +80,7 @@ export async function proxy(request: NextRequest) {
         getAll() {
           return request.cookies.getAll()
         },
-        setAll(cookiesToSet) {
+        setAll(cookiesToSet: CookiesToSet) {
           cookiesToSet.forEach(({ name, value, options }) =>
             response.cookies.set(name, value, options)
           )