feat(admin): move a customer's account to an address they can reach (#337)

The third step of the only recovery route a customer who has lost their mailbox has. The first two are contacting the shop and being verified against order history. The third had no implementation, so the answer was a hand-written database edit that left no record of who did it or why.

The thing to say plainly, because everything here follows from it: this operation and an account takeover are the same operation. They differ only in whether the verification was sound, and nothing in the software can check that. What the software can do is make the change recorded, announced, and complete in its effects.

Recorded. The endpoint refuses without a written reason, and the reason is stored against the account. That row is the only thing that tells a genuine recovery from a takeover afterwards, which is why a hand edit was never acceptable and why the field is required by the server rather than merely collected by the form. It is never shown to the customer: it is a note about how somebody was verified and can name things the customer should not be handed back.

There is no column for who did it. Admin access is one shared gate secret in front of a single operator, so such a column could only ever hold a constant, and a constant dressed up as an identity is worse than an honest absence.

Announced, to the address being replaced. If the recovery was sound that reaches nobody and costs nothing. If it was not, it reaches the real owner, who is the only person in the world who can say so, and that is the only reason this endpoint is safe to have at all. Its own template rather than the self-service one, because that copy says to contact us if you did not make this change, and here somebody already did — the sentence would be addressed to the customer who just did the thing it asks for, while the person who needs to act on it did nothing.

The new address is marked unverified and sent a confirmation link. Somebody reading an address out over the phone has not demonstrated they can receive mail at it, and that is the commonest way this goes wrong harmlessly.

Complete in its effects. The move signs the customer out everywhere, removes every passkey, and cancels reset links already sent. That is the conclusion #42 reached for password reset, and it applies here with more force: somebody the system cannot identify asked for this change, so a session or a credential surviving it is one the new owner cannot see and cannot revoke, and a reset link sitting in the mailbox being taken away would let whoever still reads it take the account straight back.

The password is left alone. What the customer lost was the mailbox, so demanding a new one adds a step for no gain.

The verification-email helper moved out of the customers route into its own module, for the reason session creation moved out for passkeys: two implementations that agree today are two that can be changed one at a time, and the one that gets forgotten is whichever the manual testing does not exercise. This path runs perhaps once a year, so it is exactly the one that would rot.

The admin drawer gains the action next to the address rather than among the account controls, because it is a thing done to that field by someone already looking at it. It leads with the warning instead of burying it. The history of moves sits on the same drawer and renders nothing at all for the overwhelming majority of customers, who have never been moved.

Verified: backend tsc clean for src and tests, 526 unit tests pass, lint clean apart from warnings that predate this branch; frontend tsc, lint and build clean. The integration suite needs a database this machine has no Docker for. It also cannot be proven by CI right now — run 917 has been hung since it started and 24 runs are queued behind it, which is the same hang #154 identifies as the source of the leftover Postgres containers.

Closes #337

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

docs/ops/account-recovery.md

@@ -14,7 +14,7 @@ safety net.
 | Their password | A reset link emailed to them | Yes |
 | Their passkey or the device holding it | Signing in with their password | Yes |
 | Every passkey and their password | A reset link emailed to them | Yes |
-| Access to their email address | Nothing. See below. | No |
+| Access to their email address | Contacting the shop, which moves the account | No |
 
 The email address is the root of trust. Every self-service route above ends at
 it, and none of them can work without it.
@@ -91,12 +91,46 @@ The route is manual, and it runs through the shop owner:
 1. The customer makes contact by whatever means they have.
 2. The owner verifies them against order history — items bought, dates, the
    shipping address on file. A stranger has none of that.
-3. The owner changes the address on the account.
+3. The owner opens the customer in Admin, Customers, and uses **Move to a new
+   address** on the detail drawer.
 
-**Step 3 does not exist yet.** The admin customer screen can disable, enable and
-release reservations, but it cannot change an email address. Until it does, the
-answer to a locked-out customer is a database edit by hand. That gap is worth
-its own issue rather than being smuggled into the passkeys project, because it
-is an admin capability with its own audit and notification questions — the
-customer whose address is being replaced has to be told, exactly as the
-self-service change already tells them.
+Step 3 was added by #337. Before it existed the only answer was a database edit
+by hand, which left no record of who did it or why.
+
+### What the move does, and why
+
+Say plainly what it is: **this operation and an account takeover are the same
+operation.** They differ only in whether the verification in step 2 was sound,
+and nothing in the software can check that. Everything the move does is aimed at
+that fact.
+
+- **It asks for a written reason, and refuses without one.** The reason is
+  recorded against the account and never shown to the customer. It is the only
+  thing that distinguishes a genuine recovery from a takeover afterwards.
+- **It emails the address being replaced.** If the recovery was sound this
+  reaches nobody, which costs nothing. If it was not, it reaches the real owner,
+  who is the only person who can say so. That mail has its own wording, because
+  the self-service notice says "if you did not make this change, contact us" and
+  here somebody already did.
+- **It sends a confirmation link to the new address and marks it unverified.** A
+  customer reading an address out over the phone has not demonstrated they can
+  receive mail at it. This is the commonest way the move goes wrong harmlessly.
+- **It signs the customer out everywhere, removes every passkey, and cancels
+  outstanding reset links.** Same reasoning as a password reset, with more
+  force: somebody the system cannot identify asked for this, so a session or
+  credential surviving it is one the new owner cannot see or revoke, and a reset
+  link sitting in the old mailbox would let whoever reads it take the account
+  straight back.
+- **It does not change the password.** What the customer lost was the mailbox,
+  not the password, so demanding a new one adds a step for no gain.
+
+The history of moves on an account is shown on the same drawer, with the reasons.
+It renders nothing at all for the overwhelming majority of customers, who have
+never been moved.
+
+### What it still does not do
+
+There is no per-admin identity to record. Admin access is one shared gate secret
+in front of a single operator, so a "who" column could only ever hold a constant,
+and a constant dressed up as an identity is worse than an honest absence. If
+per-admin identity ever arrives, the record gains a column then.