Add printable report cards, progress reports and invoices

Three documents, all print-styled rather than generated server-side: no
PDF dependency is added, and "Save as PDF" in the browser produces the
file. @media print in styles.css strips the app chrome (.no-print) and
breaks each student onto its own sheet (.print-page).

- Report card: weighted category breakdown, overall percent and letter
  from the existing gradebook config, plus an attendance summary.
- Academic progress report: the same, plus assignment-level detail —
  a mid-term report is only actionable with the underlying work listed.
- 504 / IEP progress report: each goal's baseline, target, status and
  progress entries within the period, for the quarterly report IDEA
  requires. RLS keeps it to the case manager, admins and parents.
- Invoice, reachable per student from the tuition ledger: opening
  balance carried forward, itemised activity, and balance due.

Grade maths is reused from lib/grades and the class grading config from
useEffectiveConfig, so report cards cannot drift from the gradebook.

The "Email to parents" button opens a prefilled mailto: draft — the same
mechanism the intake-link share already uses. It gathers addresses from
intake guardians and linked parent accounts. mailto cannot attach a file,
so the itemisation goes in the body as text; sending a real attachment
would need a transactional email provider and an API key.

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

src/styles.css

@@ -142,3 +142,50 @@
     color: var(--color-foreground);
   }
 }
+
+/* ── Print: report cards, progress reports, invoices ────────────────────────
+   Documents are ordinary pages on screen; @media print strips the app chrome
+   so what lands on paper (or in "Save as PDF") is just the document. Mark app
+   furniture with .no-print, and wrap each student's document in .print-page so
+   a batch of report cards breaks one-per-sheet. */
+@page {
+  margin: 14mm;
+}
+
+@media print {
+  .no-print {
+    display: none !important;
+  }
+
+  html,
+  body {
+    background: #fff !important;
+  }
+
+  /* The authenticated layout scrolls <main>; printing needs it to overflow. */
+  main {
+    overflow: visible !important;
+  }
+
+  .print-doc {
+    border: 0 !important;
+    box-shadow: none !important;
+    padding: 0 !important;
+    max-width: none !important;
+  }
+
+  .print-page + .print-page {
+    break-before: page;
+  }
+
+  tr,
+  td,
+  th {
+    break-inside: avoid;
+  }
+
+  a {
+    color: inherit;
+    text-decoration: none;
+  }
+}