Manage a person's account and teams from one page

The Admin tab could make somebody an administrator and disable them, and
nothing else. Setting a first password, deleting an account and seeing
which teams a person is in all meant curl, and the last one meant opening
each team in turn — the Team tab answers "who is in this team", which is
the wrong way round when the question is about a person.

A name in the user list now opens /admin/users/{id}: their email and when
they joined, where their notifications go, the administrator and disabled
flags, the teams they are in with their role in each, a password field
for a first or forgotten one, and deletion. A section of its own rather
than an expanding row, because memberships and the account actions
together are more than a table row can hold and still be read on a phone.

Adding somebody mints an invite link into a chosen team rather than
creating a bare account. POST /api/users makes a user with no password
and no team, who can sign in nowhere and would see nothing if they did;
the invite machinery from #7 already solves both, and the password is
chosen by the person it belongs to instead of passing through an
administrator.

One new endpoint, GET /api/users/{id}/teams, self or admin. /api/teams is
always about the caller and cannot be asked about anybody else. It 404s
for a user who does not exist, so the page can tell "in no teams" from
"no such person" — an empty list is a real answer and needed to stay one.

No authorisation changed, and the interesting part is why it did not.
requireTeamOwner has accepted the administrator flag since a4fbd60, with
the reason in its own comment: somebody has to be able to repair a team
whose owner has left. It guards nine call sites, so an administrator has
always been able to configure any team on this server — while #1's
decision table and this README both said an admin "is not implicitly in
every team", full stop. The code was right and the prose was wrong in the
safe-sounding direction, which is the worse way round to have it.

So the documentation moved to meet the code. The Teams table marks owner
as owner-or-admin, and the Authentication section states the two
directions separately: an administrator configures any team, and reads
none, because callerTeamIDs is built from real memberships only. Joining
a team to see its queue is a membership change and shows as one.

TestAdmin_ConfiguresATeamTheyAreNotIn pins both halves — the admin
renames, invites, adds and removes on a team they are not in, then sees
zero of its incidents. Nothing tested this from v0.12.0 to here, which is
why four releases of prose could contradict it quietly.

The UI has not been opened in a browser. Its wiring is checked — every
cross-module import resolves, every api.* call exists, every CSS class
has a rule, and the deep link serves index.html — but nobody has clicked
through it, least of all at phone width.

Claude-Session: https://claude.ai/code/session_01RHPj4ggeFdEjKKfm4SHbD7

internal/api/admin_test.go

@@ -237,6 +237,125 @@ func TestAdmin_GrantAndRevokeChangeWhatIsAllowed(t *testing.T) {
 	}
 }
 
+// An administrator passes every team-owner check without being in the team,
+// which is what lets them repair a team whose owner has left. It has been true
+// since teams landed and nothing pinned it, so a later reading of the epic's
+// "an admin is not implicitly in every team" could quietly take it away.
+//
+// The line it draws: configuring a team, yes; reading what the team owns, no.
+// The queue below is the half that stays shut.
+func TestAdmin_ConfiguresATeamTheyAreNotIn(t *testing.T) {
+	s := newTS(t)
+
+	// A team the admin is deliberately not a member of. It is created by
+	// somebody else, so the admin's only claim on it is the flag.
+	_, call := member(t, s, "founder")
+	var team struct {
+		ID int64 `json:"id"`
+	}
+	decode(t, call(http.MethodPost, "/api/teams", map[string]string{"name": "theirs"}), &team)
+	if team.ID == 0 {
+		t.Fatal("no team was created")
+	}
+
+	var mine []struct {
+		ID int64 `json:"id"`
+	}
+	decode(t, s.req(t, http.MethodGet, "/api/teams", nil), &mine)
+	for _, m := range mine {
+		if m.ID == team.ID {
+			t.Fatalf("the admin should not be a member of team %d", team.ID)
+		}
+	}
+
+	path := "/api/teams/" + id64(team.ID)
+	for _, c := range []struct {
+		name   string
+		method string
+		path   string
+		body   any
+		want   int
+	}{
+		{"rename it", http.MethodPut, path,
+			map[string]string{"name": "theirs, renamed"}, http.StatusNoContent},
+		{"mint an invite", http.MethodPost, path + "/invites",
+			map[string]any{"role": "member", "max_uses": 1}, http.StatusCreated},
+		{"add a member", http.MethodPost, path + "/members",
+			map[string]any{"user_id": 1, "role": "member"}, http.StatusNoContent},
+		{"remove a member", http.MethodDelete, path + "/members/1", nil, http.StatusNoContent},
+	} {
+		resp := s.req(t, c.method, c.path, c.body)
+		resp.Body.Close()
+		if resp.StatusCode != c.want {
+			t.Errorf("%s: expected %d, got %d", c.name, c.want, resp.StatusCode)
+		}
+	}
+
+	// The other half of the rule. An incident in that team is not the admin's
+	// to read, because administration is about accounts — and the last case
+	// above has just taken the admin back out of the membership.
+	var integration struct {
+		Key string `json:"key"`
+	}
+	decode(t, call(http.MethodPost, path+"/integrations",
+		map[string]string{"name": "theirs alertmanager"}), &integration)
+	postToIntegration(t, s, integration.Key, "fp-theirs", "TheirDiskFull")
+
+	var incidents []struct {
+		ID int64 `json:"id"`
+	}
+	decode(t, s.req(t, http.MethodGet, "/api/incidents", nil), &incidents)
+	if len(incidents) != 0 {
+		t.Errorf("the admin should see none of that team's incidents, got %d", len(incidents))
+	}
+}
+
+// The admin page's per-user view asks what somebody is in. Self or admin, like
+// the rest of the per-user endpoints.
+func TestUserTeams_SelfOrAdmin(t *testing.T) {
+	s := newTS(t)
+	memberID, call := member(t, s, "joiner")
+	path := "/api/users/" + id64(memberID) + "/teams"
+
+	// member() puts them in the default team, so both readings agree on one.
+	for _, c := range []struct {
+		name string
+		do   func() *http.Response
+	}{
+		{"the admin reading somebody else's", func() *http.Response { return s.req(t, http.MethodGet, path, nil) }},
+		{"the user reading their own", func() *http.Response { return call(http.MethodGet, path, nil) }},
+	} {
+		var teams []struct {
+			ID   int64  `json:"id"`
+			Name string `json:"name"`
+			Role string `json:"role"`
+		}
+		decode(t, c.do(), &teams)
+		if len(teams) != 1 {
+			t.Fatalf("%s: expected 1 team, got %d", c.name, len(teams))
+		}
+		if teams[0].Role != "member" {
+			t.Errorf("%s: expected role member, got %q", c.name, teams[0].Role)
+		}
+	}
+
+	// Somebody else's is not theirs to read.
+	otherID, _ := member(t, s, "nosy")
+	resp := call(http.MethodGet, "/api/users/"+id64(otherID)+"/teams", nil)
+	resp.Body.Close()
+	if resp.StatusCode != http.StatusForbidden {
+		t.Errorf("reading another user's teams: expected 403, got %d", resp.StatusCode)
+	}
+
+	// A user who does not exist is a 404 rather than an empty list, which is
+	// how the page tells "no teams" from "no such person".
+	resp = s.req(t, http.MethodGet, "/api/users/9999/teams", nil)
+	resp.Body.Close()
+	if resp.StatusCode != http.StatusNotFound {
+		t.Errorf("a missing user: expected 404, got %d", resp.StatusCode)
+	}
+}
+
 // The flag has to reach the client, or the web UI cannot decide what to show.
 func TestAdmin_MeReportsTheFlag(t *testing.T) {
 	s := newTS(t)