feat(auth): phase 3 — replace Supabase GoTrue with bcryptjs+jose

Custom auth stack: bcryptjs password hashing (cost 10, GoTrue-compatible),
jose JWT session cookies (edge-safe, 8hr TTL), new API routes for
login/logout/reset/change-password, middleware rewritten to JWT-only
verification with no DB access. All 38 protected pages and API routes
migrated from supabase.auth.getUser() to getSession(). Supabase .from()
queries retained for Phase 4. lib/db/index.ts refactored to lazy Proxy
singleton to avoid module-level throw during Next.js build.

tsc: clean, build: clean, tests: 4/4 passed

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

app/api/settings/route.ts

@@ -2,6 +2,7 @@ export const dynamic = 'force-dynamic'
 
 import { NextRequest, NextResponse } from 'next/server'
 import { createClient } from '@/lib/supabase/server'
+import { getSession } from '@/lib/auth/get-session'
 
 const ALLOWED_KEYS = [
   'DEEPSEEK_API_KEY',
@@ -11,18 +12,11 @@ const ALLOWED_KEYS = [
 ] as const
 type SettingKey = typeof ALLOWED_KEYS[number]
 
-async function requireAdmin(supabase: Awaited<ReturnType<typeof createClient>>) {
-  const { data: { user }, error } = await supabase.auth.getUser()
-  if (error || !user) return null
-  const { data: profile } = await supabase.from('users').select('role').eq('id', user.id).single()
-  if (!profile || profile.role !== 'admin') return null
-  return user
-}
-
 export async function GET() {
+  const session = await getSession()
+  if (!session || session.role !== 'admin') return NextResponse.json({ error: 'Forbidden' }, { status: 403 })
+
   const supabase = await createClient()
-  const user = await requireAdmin(supabase)
-  if (!user) return NextResponse.json({ error: 'Forbidden' }, { status: 403 })
 
   const { data } = await supabase.from('app_settings').select('key, value, updated_at')
   const masked = (data ?? []).map(row => ({
@@ -35,9 +29,10 @@ export async function GET() {
 }
 
 export async function POST(request: NextRequest) {
+  const session = await getSession()
+  if (!session || session.role !== 'admin') return NextResponse.json({ error: 'Forbidden' }, { status: 403 })
+
   const supabase = await createClient()
-  const user = await requireAdmin(supabase)
-  if (!user) return NextResponse.json({ error: 'Forbidden' }, { status: 403 })
 
   let body: { key?: string; value?: string }
   try { body = await request.json() } catch {
@@ -55,13 +50,13 @@ export async function POST(request: NextRequest) {
     key: body.key,
     value: body.value,
     updated_at: new Date().toISOString(),
-    updated_by: user.id,
+    updated_by: session.sub,
   })
   if (error) return NextResponse.json({ error: 'Save failed' }, { status: 500 })
 
   await supabase.rpc('write_audit_log', {
     p_table_name: 'app_settings',
-    p_record_id: user.id,
+    p_record_id: session.sub,
     p_action: 'UPDATE',
     p_new_value: { key: body.key, set: Boolean(body.value) } as never,
   })