Phase 9c: Parent accounts, magic-link login + parent timetable view

Backend (school-service):
  - parent_account, parent_child, parent_magic_link, parent_session
    tables. Tokens are sha256-hashed in DB; raw goes back exactly
    once to the inviting teacher.
  - InviteParent upserts the parent account, links a child to a tt_
    class, mints a 7-day magic link. Returns the link path so the
    teacher can paste it into Matrix/Email.
  - RedeemMagicLink validates + marks used + mints a 30-day session,
    sets HttpOnly bp_parent_session cookie.
  - ParentSessionMiddleware reads the cookie and resolves the parent.
    Lives in its own router group /api/v1/parent — totally separate
    from the teacher JWT path.
  - ParentMe returns the account + list of children (with class name).
  - ParentTimetable returns the latest completed tt_solution's lessons
    for the requested child's class, with full authorization check
    (parent must own a child in that class).

Frontend (studio-v2):
  - lib/calendar/subject-i18n.ts maps 22 German subject names to 8
    parent locales (de/en/tr/ar/uk/ru/pl/fr). Falls back to German
    for custom subjects.
  - ParentManager component on the Schulkalender page lets the teacher
    invite parents via email + child name + class + language. Newly
    minted magic-link is shown with a copy-to-clipboard button.
  - app/api/parent/[...path]/route.ts proxies parent-side endpoints
    via the cookie so HttpOnly survives the Next.js round-trip.
  - /eltern/login?token=… redeems and redirects to /eltern.
  - /eltern shows a Wochengrid with German days + translated subject
    names in the parent's preferred language. Headings and weekday
    labels also localised (de/en/tr/ar/uk/ru/pl/fr).

Tests:
  - 3 new Go unit tests (random token, hash stability, invite-request
    validator). 83 subtests gesamt.
  - studio-v2: e2e/eltern.spec.ts mit 7 tests across ParentManager,
    /eltern/login, /eltern overview, subject-i18n end-to-end.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

school-service/internal/models/parent.go

@@ -0,0 +1,76 @@
+package models
+
+import (
+	"time"
+
+	"github.com/google/uuid"
+)
+
+type ParentAccount struct {
+	ID                uuid.UUID `json:"id" db:"id"`
+	CreatedByUserID   uuid.UUID `json:"created_by_user_id" db:"created_by_user_id"`
+	Email             string    `json:"email" db:"email"`
+	PreferredLanguage string    `json:"preferred_language" db:"preferred_language"`
+	CreatedAt         time.Time `json:"created_at" db:"created_at"`
+}
+
+type ParentChild struct {
+	ID         uuid.UUID `json:"id" db:"id"`
+	ParentID   uuid.UUID `json:"parent_id" db:"parent_id"`
+	TTClassID  uuid.UUID `json:"tt_class_id" db:"tt_class_id"`
+	FirstName  string    `json:"first_name" db:"first_name"`
+	LastName   string    `json:"last_name" db:"last_name"`
+	CreatedAt  time.Time `json:"created_at" db:"created_at"`
+	// Joined for display
+	ClassName  string    `json:"class_name,omitempty"`
+}
+
+// Request DTOs
+
+// InviteParentRequest is what the teacher posts to invite one parent for one
+// child. The endpoint creates the account if it doesn't exist, the child
+// row, and a fresh magic_link. Same parent can be invited for several
+// children (re-using the account).
+type InviteParentRequest struct {
+	Email             string `json:"email" binding:"required,email"`
+	PreferredLanguage string `json:"preferred_language"`
+	ChildFirstName    string `json:"child_first_name" binding:"required"`
+	ChildLastName     string `json:"child_last_name" binding:"required"`
+	TTClassID         string `json:"tt_class_id" binding:"required,uuid"`
+}
+
+// InviteParentResponse carries the freshly-minted magic-link path so the
+// teacher can copy it into Matrix/Email manually (mass-send comes from the
+// notification worker in Phase 9d).
+type InviteParentResponse struct {
+	Parent     ParentAccount `json:"parent"`
+	Child      ParentChild   `json:"child"`
+	MagicToken string        `json:"magic_token"`
+	MagicURL   string        `json:"magic_url"`
+	ExpiresAt  time.Time     `json:"expires_at"`
+}
+
+// ParentInviteListItem is the teacher-facing list row — one entry per
+// (parent, child) pair, with the joined class name.
+type ParentInviteListItem struct {
+	ParentID          uuid.UUID `json:"parent_id"`
+	Email             string    `json:"email"`
+	PreferredLanguage string    `json:"preferred_language"`
+	ChildID           uuid.UUID `json:"child_id"`
+	ChildFirstName    string    `json:"child_first_name"`
+	ChildLastName     string    `json:"child_last_name"`
+	ClassID           uuid.UUID `json:"class_id"`
+	ClassName         string    `json:"class_name"`
+	CreatedAt         time.Time `json:"created_at"`
+}
+
+// RedeemMagicLinkRequest is what /parent/auth/redeem expects.
+type RedeemMagicLinkRequest struct {
+	Token string `json:"token" binding:"required"`
+}
+
+// ParentMe is what /parent/me returns: the account + every linked child.
+type ParentMe struct {
+	Parent   ParentAccount  `json:"parent"`
+	Children []ParentChild  `json:"children"`
+}