fix: Restore all files lost during destructive rebase

A previous `git pull --rebase origin main` dropped 177 local commits,
losing 3400+ files across admin-v2, backend, studio-v2, website,
klausur-service, and many other services. The partial restore attempt
(660295e2) only recovered some files.

This commit restores all missing files from pre-rebase ref 98933f5e
while preserving post-rebase additions (night-scheduler, night-mode UI,
NightModeWidget dashboard integration).

Restored features include:
- AI Module Sidebar (FAB), OCR Labeling, OCR Compare
- GPU Dashboard, RAG Pipeline, Magic Help
- Klausur-Korrektur (8 files), Abitur-Archiv (5+ files)
- Companion, Zeugnisse-Crawler, Screen Flow
- Full backend, studio-v2, website, klausur-service
- All compliance SDKs, agent-core, voice-service
- CI/CD configs, documentation, scripts

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

backend/frontend/static/css/modules/admin/preview.css

@@ -0,0 +1,202 @@
+/* ==========================================
+   ADMIN PANEL - Preview & Compare
+   Image preview, document comparison
+   ========================================== */
+
+.compare-header {
+  background: var(--bp-surface-elevated);
+  padding: 6px 10px;
+  font-size: 12px;
+  border-bottom: 1px solid var(--bp-border-subtle);
+  display: flex;
+  justify-content: space-between;
+  align-items: center;
+  gap: 6px;
+}
+
+.compare-header span {
+  color: var(--bp-text-muted);
+}
+
+.compare-body {
+  flex: 1;
+  min-height: 0;
+  position: relative;
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  padding: 6px;
+}
+
+.compare-body-inner {
+  position: relative;
+  width: 100%;
+  height: 100%;
+  display: flex;
+  align-items: center;
+  justify-content: center;
+}
+
+.preview-img {
+  max-width: 100%;
+  max-height: 100%;
+  object-fit: contain;
+  box-shadow: 0 18px 40px rgba(0,0,0,0.5);
+  border-radius: 10px;
+}
+
+.clean-frame {
+  width: 100%;
+  height: 100%;
+  border: none;
+  border-radius: 10px;
+  background: white;
+}
+
+/* Preview Navigation */
+.preview-nav {
+  position: absolute;
+  inset: 0;
+  display: flex;
+  align-items: center;
+  justify-content: space-between;
+  pointer-events: none;
+  padding: 0 4px;
+}
+
+.preview-nav button {
+  pointer-events: auto;
+  width: 28px;
+  height: 28px;
+  border-radius: 999px;
+  border: 1px solid var(--bp-border-subtle);
+  background: var(--bp-surface-elevated);
+  color: var(--bp-text);
+  cursor: pointer;
+  font-size: 14px;
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  transition: all 0.2s ease;
+}
+
+.preview-nav button:hover:not(:disabled) {
+  border-color: var(--bp-primary);
+  color: var(--bp-primary);
+}
+
+.preview-nav button:disabled {
+  opacity: 0.35;
+  cursor: default;
+}
+
+.preview-nav span {
+  position: absolute;
+  bottom: 6px;
+  left: 50%;
+  transform: translateX(-50%);
+  font-size: 11px;
+  padding: 2px 8px;
+  border-radius: 999px;
+  background: var(--bp-surface-elevated);
+  border: 1px solid var(--bp-border-subtle);
+}
+
+/* Preview Thumbnails */
+.preview-thumbnails {
+  display: flex;
+  flex-direction: column;
+  gap: 8px;
+  padding: 8px 4px;
+  overflow-y: auto;
+  align-items: center;
+}
+
+.preview-thumb {
+  min-width: 90px;
+  width: 90px;
+  height: 70px;
+  border-radius: 8px;
+  border: 2px solid rgba(148,163,184,0.25);
+  background: rgba(15,23,42,0.5);
+  cursor: pointer;
+  overflow: hidden;
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  position: relative;
+  flex-shrink: 0;
+}
+
+.preview-thumb:hover {
+  border-color: var(--bp-accent);
+}
+
+.preview-thumb.active {
+  border-color: var(--bp-accent);
+  border-width: 3px;
+}
+
+.preview-thumb img {
+  width: 100%;
+  height: 100%;
+  object-fit: cover;
+}
+
+.preview-thumb-label {
+  position: absolute;
+  bottom: 0;
+  left: 0;
+  right: 0;
+  font-size: 9px;
+  padding: 2px;
+  background: rgba(0,0,0,0.8);
+  color: white;
+  text-align: center;
+  white-space: nowrap;
+  overflow: hidden;
+  text-overflow: ellipsis;
+}
+
+/* Light Mode */
+[data-theme="light"] .compare-header {
+  background: var(--bp-primary-soft);
+  border-bottom: 1px solid var(--bp-primary);
+}
+
+[data-theme="light"] .compare-header span {
+  color: var(--bp-primary);
+  font-weight: 600;
+}
+
+[data-theme="light"] .preview-img {
+  box-shadow: 0 8px 24px rgba(14, 165, 233, 0.15);
+}
+
+[data-theme="light"] .preview-nav button {
+  border: 2px solid var(--bp-primary);
+  background: var(--bp-surface);
+  color: var(--bp-primary);
+  font-weight: 700;
+}
+
+[data-theme="light"] .preview-nav button:hover:not(:disabled) {
+  background: var(--bp-primary);
+  color: white;
+}
+
+[data-theme="light"] .preview-nav span {
+  background: var(--bp-surface);
+  border: 1px solid var(--bp-primary);
+  color: var(--bp-primary);
+}
+
+[data-theme="light"] .preview-thumb {
+  background: var(--bp-bg);
+  border-color: var(--bp-border);
+}
+
+[data-theme="light"] .preview-thumb:hover,
+[data-theme="light"] .preview-thumb.active {
+  border-color: var(--bp-primary);
+}