feat: add Legal Translation tool (translate.php)

New dedicated tool for translating Norwegian legal documents (Barnevernet
letters, court decisions, correspondence) into the user's chosen language
with legal-terminology annotations.

- translate.php: new tool page with source/target language selectors,
  4-way UI lang switcher, file upload, doc picker, streaming results
- api/translate.php: NDJSON streaming endpoint; Azure GPT-4o-mini with
  legal-aware prompt that preserves Norwegian statute refs verbatim and
  annotates terms with no target-language equivalent; 2-credit cost
- assets/js/translate.js: form handler, NDJSON stream reader, copy button
- assets/css/tools.css: .lt-* styles for translation result + annotations
- includes/i18n.php: 22 lt_* keys × 4 languages; translate entry in nav
- includes/FreeTier.php: translate → 2 credits
- includes/CaseResults.php + case-result.php: translate in eligible tools,
  toolLabel, toolIcon, deriveTitle, rendering block, rerun map

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

assets/css/tools.css

@@ -9397,3 +9397,57 @@ body.lt-landing {
 }
 .la-synthesis h3 { margin-top: 0; color: #0e7490; }
 .la-synthesis h4 { margin: 0.9rem 0 0.4rem; font-size: 0.95rem; color: #155e75; }
+
+/* ── Legal Translation ─────────────────────────────────────────────────── */
+.lt-source-target-row { display: flex; gap: 1.5rem; align-items: center; flex-wrap: wrap; margin-bottom: 0.75rem; }
+.lt-source-target-row .control-label { min-width: 8rem; font-weight: 600; }
+.lt-result { margin-bottom: 1.4rem; }
+.lt-result__head {
+  display: flex;
+  align-items: center;
+  gap: 0.75rem;
+  flex-wrap: wrap;
+  margin-bottom: 0.75rem;
+}
+.lt-result__head h3 { margin: 0; }
+.lt-lang-pair {
+  font-size: 0.8rem;
+  font-family: monospace;
+  background: var(--surface-2, #f1f5f9);
+  border: 1px solid var(--border, #cbd5e1);
+  border-radius: 4px;
+  padding: 0.2rem 0.5rem;
+  color: #475569;
+}
+.lt-translated-text {
+  white-space: pre-wrap;
+  font-size: 0.95rem;
+  line-height: 1.75;
+  border: 1px solid var(--border, #cbd5e1);
+  border-radius: 8px;
+  padding: 1.25rem 1.5rem;
+  background: var(--surface-2, #f8fafc);
+  color: #1e293b;
+  max-height: 60vh;
+  overflow-y: auto;
+}
+.lt-copy-btn {
+  margin-left: auto;
+  font-size: 0.83rem;
+  padding: 0.3rem 0.75rem;
+}
+.lt-annotations { margin-top: 1.5rem; }
+.lt-annotations h4 { margin: 0 0 0.6rem; font-size: 0.9rem; color: #475569; }
+.lt-annotation {
+  background: var(--surface-2, #f8fafc);
+  border-left: 3px solid var(--accent, #0f766e);
+  padding: 0.45rem 0.75rem;
+  margin-bottom: 0.45rem;
+  border-radius: 0 6px 6px 0;
+  font-size: 0.87rem;
+  line-height: 1.5;
+  color: #334155;
+}
+.lt-annotation strong { font-family: monospace; color: #0e7490; }
+.lt-busy { padding: 2rem; text-align: center; color: #64748b; animation: pulse 1.5s ease-in-out infinite; }
+@keyframes pulse { 0%, 100% { opacity: 1; } 50% { opacity: 0.5; } }