feat: require current password when changing password, add zxcvbn strength check

Use PasswordChange model (requires current password) for users with
existing passwords and PasswordSet for first-time setup. Add zxcvbn
strength validation and current password field to credentials template.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

tests/test_password_change.py

@@ -0,0 +1,125 @@
+from datetime import UTC, datetime
+
+import pytest
+from httpx import AsyncClient
+
+from porchlight.authn.password import PasswordHasher, PasswordService
+from porchlight.models import PasswordCredential, User
+
+from tests.conftest import get_csrf_token
+
+
+async def _login_user_with_password(client: AsyncClient) -> str:
+    """Create user with password, login, return CSRF token."""
+    app = client._transport.app
+    user_repo = app.state.user_repo
+    cred_repo = app.state.credential_repo
+
+    user = User(
+        userid="pw-user-01",
+        username="pwuser",
+        created_at=datetime.now(UTC),
+        updated_at=datetime.now(UTC),
+    )
+    await user_repo.create(user)
+
+    svc = PasswordService(hasher=PasswordHasher(time_cost=1, memory_cost=8192))
+    await cred_repo.create_password(
+        PasswordCredential(user_id=user.userid, password_hash=svc.hash("OldPass123!ok"))
+    )
+
+    token = await get_csrf_token(client)
+    await client.post(
+        "/login/password",
+        data={"username": "pwuser", "password": "OldPass123!ok"},
+        headers={"HX-Request": "true", "X-CSRF-Token": token},
+    )
+    return token
+
+
+async def _login_user_without_password(client: AsyncClient) -> str:
+    """Create user without password, simulate session login, return CSRF token."""
+    app = client._transport.app
+    user_repo = app.state.user_repo
+
+    user = User(
+        userid="pw-user-02",
+        username="newuser",
+        created_at=datetime.now(UTC),
+        updated_at=datetime.now(UTC),
+    )
+    await user_repo.create(user)
+
+    # Simulate session login via magic link
+    token = await get_csrf_token(client)
+    magic_link_service = app.state.magic_link_service
+    link = await magic_link_service.create(username="newuser", created_by="admin", note="test")
+    await client.get(f"/register/{link.token}", follow_redirects=False)
+    # Re-fetch CSRF token after session change
+    token = await get_csrf_token(client)
+    return token
+
+
+@pytest.mark.asyncio
+async def test_change_password_requires_current(client: AsyncClient) -> None:
+    token = await _login_user_with_password(client)
+
+    response = await client.post(
+        "/manage/credentials/password",
+        data={
+            "password": "NewStrong!Pass99",
+            "confirm": "NewStrong!Pass99",
+        },
+        headers={"X-CSRF-Token": token},
+    )
+    assert "alert" in response.text
+    assert "urrent password" in response.text
+
+
+@pytest.mark.asyncio
+async def test_change_password_wrong_current_rejected(client: AsyncClient) -> None:
+    token = await _login_user_with_password(client)
+
+    response = await client.post(
+        "/manage/credentials/password",
+        data={
+            "current_password": "WrongPassword",
+            "password": "NewStrong!Pass99",
+            "confirm": "NewStrong!Pass99",
+        },
+        headers={"X-CSRF-Token": token},
+    )
+    assert "alert" in response.text
+    assert "incorrect" in response.text.lower() or "Invalid" in response.text or "current" in response.text.lower()
+
+
+@pytest.mark.asyncio
+async def test_change_password_correct_current_succeeds(client: AsyncClient) -> None:
+    token = await _login_user_with_password(client)
+
+    response = await client.post(
+        "/manage/credentials/password",
+        data={
+            "current_password": "OldPass123!ok",
+            "password": "NewStrong!Pass99",
+            "confirm": "NewStrong!Pass99",
+        },
+        headers={"X-CSRF-Token": token},
+    )
+    assert "updated" in response.text.lower() or "status" in response.text
+
+
+@pytest.mark.asyncio
+async def test_set_password_no_current_needed(client: AsyncClient) -> None:
+    """First-time password setup should not require current password."""
+    token = await _login_user_without_password(client)
+
+    response = await client.post(
+        "/manage/credentials/password",
+        data={
+            "password": "FirstPass!Strong99",
+            "confirm": "FirstPass!Strong99",
+        },
+        headers={"X-CSRF-Token": token},
+    )
+    assert "updated" in response.text.lower() or "status" in response.text