Add SFV panel: compute/verify CRC32/MD5/SHA1 checksums, .sfv/.md5/.sha1 sidecar files

Fully local feature - no network access, no credentials. New aurora-curator-core::sfv
module streams file hashing in 64KB chunks and handles both the traditional .sfv
format (CRC32, "name checksum" layout) and the GNU coreutils md5sum/sha1sum sidecar
convention (.md5/.sha1, "checksum  name" layout), dispatched on a shared ChecksumKind
enum. New src-tauri/src/sfv.rs wraps it in three Tauri commands - compute_checksums
(per-file error isolation), save_checksum_file (native Save dialog), and
verify_checksum_file (resolves each entry against the checksum file's own parent
directory, reports OK/Mismatch/Missing per entry). New SfvPanel.tsx/.css wires it all
into the sidebar's SFV screen - load files, pick a checksum type, Compute, Save, or
Verify against an existing checksum file.

14 new core-crate tests + 1 new src-tauri test, all passing (workspace: 160/160).
Verified end-to-end with a 22-check Playwright script against npm run dev.

src/components/SfvPanel.css

@@ -0,0 +1,105 @@
+.sfv-panel {
+  height: 100%;
+  min-width: 0;
+  display: flex;
+  flex-direction: column;
+  gap: 14px;
+  padding: 18px;
+  overflow-y: auto;
+}
+
+.sfv-toolbar {
+  display: flex;
+  align-items: center;
+  gap: 14px;
+  flex-wrap: wrap;
+  background: var(--card);
+  border: 1px solid var(--surface-deep);
+  border-radius: 12px;
+  padding: 14px;
+}
+
+.sfv-loaded-count {
+  font-size: 12px;
+  color: var(--muted-text);
+}
+
+.sfv-actions {
+  display: flex;
+  align-items: center;
+  gap: 10px;
+  flex-wrap: wrap;
+}
+
+.sfv-results {
+  flex: 1;
+  min-height: 0;
+  display: flex;
+  flex-direction: column;
+  gap: 6px;
+}
+
+.sfv-row {
+  display: flex;
+  align-items: center;
+  gap: 12px;
+  background: var(--card);
+  border: 1px solid var(--surface-deep);
+  border-radius: 10px;
+  padding: 9px 12px;
+}
+
+.sfv-row-name {
+  flex: 1;
+  min-width: 0;
+  font-size: 12.5px;
+  overflow: hidden;
+  text-overflow: ellipsis;
+  white-space: nowrap;
+}
+
+.sfv-row-checksum {
+  flex: 0 0 auto;
+  font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
+  font-size: 12px;
+  color: var(--aurora-cyan);
+}
+
+.sfv-row-checksum-muted {
+  color: var(--muted-text);
+}
+
+.sfv-badge {
+  flex: 0 0 auto;
+  font-size: 10.5px;
+  font-weight: 700;
+  letter-spacing: 0.04em;
+  border-radius: 999px;
+  padding: 3px 9px;
+}
+
+.sfv-badge-ok {
+  background: rgba(52, 211, 153, 0.16);
+  color: #34d399;
+}
+
+.sfv-badge-mismatch {
+  background: rgba(248, 113, 113, 0.16);
+  color: #f87171;
+}
+
+.sfv-badge-missing {
+  background: rgba(250, 204, 21, 0.16);
+  color: #facc15;
+}
+
+.sfv-empty-note {
+  color: var(--muted-text);
+  font-size: 12.5px;
+  padding: 8px 2px;
+}
+
+.sfv-status {
+  font-size: 12px;
+  color: var(--aurora-cyan);
+}