fix(mcp-oauth): api_keys.company_id nullable so companyless signups can mint their key (#1919)

Every fresh Claude.ai authorization died at POST /api/mcp-oauth/token
with a silent 500: the multi-tenant refactor's dynamic loop
(20260330130000, line ~250) set company_id NOT NULL on api_keys, and the
companyless key insert from the popup-signup flow (#1814) violates it.
Nothing exercised the real insert before (unit tests mock the client;
no pg test inserted an unbound key), so repo, CI and prod all agreed and
all were wrong. DROP NOT NULL, log the insert/rotation failures at the
token endpoint, and pin the unbound insert + lazy bind on real Postgres.


Claude-Session: https://claude.ai/code/session_018wCdzRTatKiDByKB8hCNT6

Co-authored-by: Jakob Wennberg <311770904+jakobwennberg-oss@users.noreply.github.com>
Co-authored-by: Claude Fable 5 <noreply@anthropic.com>

tests/pg/api-keys-unbound.pg.test.ts

@@ -0,0 +1,41 @@
+import { describe, expect, it } from 'vitest'
+import { randomUUID, createHash } from 'node:crypto'
+import { getPool } from './setup'
+import { insertAuthUser } from './fixtures'
+
+/**
+ * Unbound API keys (migration 20260826090000): a key minted from the OAuth
+ * popup before the user's first company exists carries company_id NULL.
+ * The NOT NULL from 20260330130000's dynamic loop made the token endpoint's
+ * insert fail with a plain 500 on every fresh Claude.ai authorization; a
+ * mocked client cannot see a column constraint, so this pins it on real
+ * Postgres.
+ */
+describe('api_keys unbound insert.pg', () => {
+  it('accepts a key with no company binding', async () => {
+    const userId = await insertAuthUser()
+    const keyHash = createHash('sha256').update(randomUUID()).digest('hex')
+    const inserted = await getPool().query<{ id: string; company_id: string | null }>(
+      `INSERT INTO public.api_keys (user_id, company_id, key_hash, key_prefix, name, scopes)
+       VALUES ($1, NULL, $2, 'gnubok_sk_test', 'MCP-klient (OAuth)', ARRAY['companies:read'])
+       RETURNING id, company_id`,
+      [userId, keyHash],
+    )
+    expect(inserted.rows[0]!.company_id).toBeNull()
+
+    // The lazy bind heals exactly the unbound row.
+    const companyRes = await getPool().query<{ id: string }>(
+      `SELECT public.create_company_for_user($1::uuid, 'Bind AB', 'aktiebolag', NULL) AS id`,
+      [userId],
+    )
+    await getPool().query(
+      `UPDATE public.api_keys SET company_id = $1 WHERE id = $2 AND company_id IS NULL`,
+      [companyRes.rows[0]!.id, inserted.rows[0]!.id],
+    )
+    const healed = await getPool().query<{ company_id: string | null }>(
+      `SELECT company_id FROM public.api_keys WHERE id = $1`,
+      [inserted.rows[0]!.id],
+    )
+    expect(healed.rows[0]!.company_id).toBe(companyRes.rows[0]!.id)
+  })
+})