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/auth/change-password/route.ts

@@ -0,0 +1,32 @@
+export const dynamic = 'force-dynamic'
+
+import { NextRequest, NextResponse } from 'next/server'
+import { getSession } from '@/lib/auth/get-session'
+import { asAdmin } from '@/lib/db/with-user'
+import { users } from '@/lib/db/schema'
+import { eq } from 'drizzle-orm'
+import { verifyPassword, hashPassword } from '@/lib/auth/password'
+
+export async function POST(req: NextRequest) {
+  const session = await getSession()
+  if (!session) return NextResponse.json({ error: 'Unauthorized' }, { status: 401 })
+
+  const { currentPassword, newPassword } = await req.json()
+  if (!currentPassword || !newPassword || newPassword.length < 8) {
+    return NextResponse.json({ error: 'Invalid request' }, { status: 400 })
+  }
+
+  const [user] = await asAdmin(db =>
+    db.select({ passwordHash: users.passwordHash })
+      .from(users).where(eq(users.id, session.sub)).limit(1)
+  )
+
+  if (!user || !await verifyPassword(currentPassword, user.passwordHash)) {
+    return NextResponse.json({ error: 'Current password is incorrect' }, { status: 400 })
+  }
+
+  const newHash = await hashPassword(newPassword)
+  await asAdmin(db => db.update(users).set({ passwordHash: newHash }).where(eq(users.id, session.sub)))
+
+  return NextResponse.json({ ok: true })
+}