feat(invites): team invite links — admin create/revoke, public accept (#42)

* feat(branding): white-label — public /branding, admin write, shell theming

app_settings branding.* keys (product name, logo/favicon URLs, accent
color, docs/support links). Public GET /branding so login and shell
theme pre-auth; admin writes via PUT /settings.

useBranding() applies document.title, accent CSS var and favicon;
BrandWordmark replaces hardcoded wordmarks; admin Platform settings
gain a Branding form. MCP containr_branding_get + settings_update.

Generated with [Devin](https://devin.ai)

Co-Authored-By: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>

* feat(invites): team invite links — admin create/revoke, public accept

Admins mint single-use invite links (sha256-hashed token at rest,
optional email binding, configurable TTL). Public endpoints let the
accept page validate the link and register — working even while
public signup is disabled.

- migration + sqlc queries/model for user_invites
- POST /admin/invites (returns one-time token+url), GET list, DELETE revoke
- GET /auth/invites/:token public validation, POST /auth/accept-invite
- CLI containr invites list|create|revoke; MCP invites tools
- /auth/accept-invite page (expired/used/invalid states, bound-email lock)
- Admin page Team invites section: create, copy link, revoke
- OpenAPI + generated types + CLI guide

Generated with [Devin](https://devin.ai)

Co-Authored-By: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>

---------

Co-authored-by: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>

app/backend/internal/database/sqlcdb/invites.sql.go

@@ -0,0 +1,134 @@
+// Code generated by sqlc. DO NOT EDIT.
+// versions:
+//   sqlc v1.31.1
+// source: invites.sql
+
+package sqlcdb
+
+import (
+	"context"
+	"database/sql"
+	"time"
+
+	"github.com/google/uuid"
+)
+
+const createUserInvite = `-- name: CreateUserInvite :one
+INSERT INTO user_invites (token_hash, email, created_by, expires_at)
+VALUES ($1, $2, $3, $4)
+RETURNING user_invites.id, user_invites.token_hash, user_invites.email, user_invites.created_by, user_invites.expires_at, user_invites.used_by, user_invites.used_at, user_invites.created_at
+`
+
+type CreateUserInviteParams struct {
+	TokenHash string         `json:"token_hash"`
+	Email     sql.NullString `json:"email"`
+	CreatedBy uuid.NullUUID  `json:"created_by"`
+	ExpiresAt time.Time      `json:"expires_at"`
+}
+
+func (q *Queries) CreateUserInvite(ctx context.Context, arg CreateUserInviteParams) (UserInvite, error) {
+	row := q.db.QueryRowContext(ctx, createUserInvite,
+		arg.TokenHash,
+		arg.Email,
+		arg.CreatedBy,
+		arg.ExpiresAt,
+	)
+	var i UserInvite
+	err := row.Scan(
+		&i.ID,
+		&i.TokenHash,
+		&i.Email,
+		&i.CreatedBy,
+		&i.ExpiresAt,
+		&i.UsedBy,
+		&i.UsedAt,
+		&i.CreatedAt,
+	)
+	return i, err
+}
+
+const deleteUserInvite = `-- name: DeleteUserInvite :exec
+DELETE FROM user_invites
+WHERE id = $1
+`
+
+func (q *Queries) DeleteUserInvite(ctx context.Context, id uuid.UUID) error {
+	_, err := q.db.ExecContext(ctx, deleteUserInvite, id)
+	return err
+}
+
+const getUserInviteByTokenHash = `-- name: GetUserInviteByTokenHash :one
+SELECT user_invites.id, user_invites.token_hash, user_invites.email, user_invites.created_by, user_invites.expires_at, user_invites.used_by, user_invites.used_at, user_invites.created_at
+FROM user_invites
+WHERE token_hash = $1
+`
+
+func (q *Queries) GetUserInviteByTokenHash(ctx context.Context, tokenHash string) (UserInvite, error) {
+	row := q.db.QueryRowContext(ctx, getUserInviteByTokenHash, tokenHash)
+	var i UserInvite
+	err := row.Scan(
+		&i.ID,
+		&i.TokenHash,
+		&i.Email,
+		&i.CreatedBy,
+		&i.ExpiresAt,
+		&i.UsedBy,
+		&i.UsedAt,
+		&i.CreatedAt,
+	)
+	return i, err
+}
+
+const listUserInvites = `-- name: ListUserInvites :many
+SELECT user_invites.id, user_invites.token_hash, user_invites.email, user_invites.created_by, user_invites.expires_at, user_invites.used_by, user_invites.used_at, user_invites.created_at
+FROM user_invites
+ORDER BY created_at DESC
+`
+
+func (q *Queries) ListUserInvites(ctx context.Context) ([]UserInvite, error) {
+	rows, err := q.db.QueryContext(ctx, listUserInvites)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+	items := []UserInvite{}
+	for rows.Next() {
+		var i UserInvite
+		if err := rows.Scan(
+			&i.ID,
+			&i.TokenHash,
+			&i.Email,
+			&i.CreatedBy,
+			&i.ExpiresAt,
+			&i.UsedBy,
+			&i.UsedAt,
+			&i.CreatedAt,
+		); err != nil {
+			return nil, err
+		}
+		items = append(items, i)
+	}
+	if err := rows.Close(); err != nil {
+		return nil, err
+	}
+	if err := rows.Err(); err != nil {
+		return nil, err
+	}
+	return items, nil
+}
+
+const markUserInviteUsed = `-- name: MarkUserInviteUsed :exec
+UPDATE user_invites
+SET used_by = $2, used_at = now()
+WHERE id = $1 AND used_at IS NULL
+`
+
+type MarkUserInviteUsedParams struct {
+	ID     uuid.UUID     `json:"id"`
+	UsedBy uuid.NullUUID `json:"used_by"`
+}
+
+func (q *Queries) MarkUserInviteUsed(ctx context.Context, arg MarkUserInviteUsedParams) error {
+	_, err := q.db.ExecContext(ctx, markUserInviteUsed, arg.ID, arg.UsedBy)
+	return err
+}