Remove multi-tenant company_id scoping from entire codebase

Drop company_id column from all 22 domain tables via migration.
Remove companyId from JWT payload, auth plugins, all service method
signatures (~215 occurrences), all route handlers (~105 occurrences),
test runner, test suites, and frontend auth store/types.

The company table stays as store settings (name, timezone). Tenant
isolation in a SaaS deployment would be at the database level (one
DB per customer) not the application level.

All 107 API tests pass. Zero TSC errors across all packages.

packages/backend/src/routes/v1/auth.ts

@@ -3,7 +3,6 @@ import { eq } from 'drizzle-orm'
 import bcrypt from 'bcrypt'
 import { RegisterSchema, LoginSchema } from '@forte/shared/schemas'
 import { users } from '../../db/schema/users.js'
-import { companies } from '../../db/schema/stores.js'
 
 const SALT_ROUNDS = 10
 
@@ -27,28 +26,8 @@ export const authRoutes: FastifyPluginAsync = async (app) => {
     }
 
     const { email, password, firstName, lastName, role } = parsed.data
-    const companyId = request.companyId
 
-    // Validate that the company exists
-    if (!companyId) {
-      return reply.status(400).send({
-        error: { message: 'Company ID is required (x-company-id header)', statusCode: 400 },
-      })
-    }
-
-    const [company] = await app.db
-      .select({ id: companies.id })
-      .from(companies)
-      .where(eq(companies.id, companyId))
-      .limit(1)
-
-    if (!company) {
-      return reply.status(400).send({
-        error: { message: 'Invalid company', statusCode: 400 },
-      })
-    }
-
-    // Email is globally unique across all companies
+    // Email is globally unique
     const existing = await app.db
       .select({ id: users.id })
       .from(users)
@@ -66,7 +45,6 @@ export const authRoutes: FastifyPluginAsync = async (app) => {
     const [user] = await app.db
       .insert(users)
       .values({
-        companyId,
         email,
         passwordHash,
         firstName,
@@ -84,11 +62,10 @@ export const authRoutes: FastifyPluginAsync = async (app) => {
 
     const token = app.jwt.sign({
       id: user.id,
-      companyId,
       role: user.role,
     })
 
-    request.log.info({ userId: user.id, email: user.email, companyId }, 'User registered')
+    request.log.info({ userId: user.id, email: user.email }, 'User registered')
     return reply.status(201).send({ user, token })
   })
 
@@ -126,7 +103,6 @@ export const authRoutes: FastifyPluginAsync = async (app) => {
 
     const token = app.jwt.sign({
       id: user.id,
-      companyId: user.companyId,
       role: user.role,
     })