feat(metadata): add OpenModelDB metadata provider and model source for upscalers

Add OpenModelDB (openmodeldb.info) as a metadata and download source for
the existing upscaler model type.

Metadata:
- New OpenModelDBClient: fetches the site's bulk JSON dumps, caches them
  on disk (24h TTL + ETag revalidation), and builds a local sha256 index
- New OpenModelDBModelMetadataProvider adapts catalogue entries to the
  CivitAI-shaped version dict contract; registered in the fallback chain
  behind the enable_openmodeldb_api setting (default on), gated to the
  upscaler sub-type so other model types never trigger the dump download
- Persisted provenance uses metadata_source "openmodeldb" plus a nested
  openmodeldb block (page URL, architecture, scale, license)

Images: paired-image LR/SR URLs are ephemeral imgdiff.net sessions, so
displayable images come from the site-hosted auto-generated thumbnails
(model-level cover leads images[], per-image thumbs for the rest); the
original comparison URL is kept in meta.comparisonUrl.

Downloads:
- New OpenModelDBSource (flat model ids, omdb: group prefix) with
  resource filename derivation that recovers names hidden mid-path
  (mediafire) or synthesizes {id}.{type} for folder links
- HTML-gateway mirrors (mediafire/mega/drive) are rejected with a clear
  manual-download hint instead of silently saving an HTML page as .pth
- ModelSource base gains is_valid_source_id / default_subdir_parts /
  resolve_download_url hooks so flat-id sources need no platform branches

UI: "View on OpenModelDB" link in the model modal (downloaded and
hash-enriched models), settings toggle next to the CivArchive one.

static/js/components/shared/ModelModal.js

@@ -1,5 +1,5 @@
 import { showToast, openCivitai, sendLoraToWorkflow, sendEmbeddingToWorkflow, sendModelPathToWorkflow, buildLoraSyntax, copyToClipboard } from '../../utils/uiHelpers.js';
-import { getModelSourceInfo, getModelSourceGroupKey, getModelSourceViewTitle, openModelSource } from '../../utils/modelSourceHelpers.js';
+import { getModelSource, getModelSourceInfo, getModelSourceGroupKey, getModelSourceViewTitle, openModelSource } from '../../utils/modelSourceHelpers.js';
 import { modalManager } from '../../managers/ModalManager.js';
 import { MODEL_TYPES } from '../../api/apiConfig.js';
 import {
@@ -32,6 +32,18 @@ function getModalFilePath(fallback = '') {
     return fallback;
 }
 
+/**
+ * Source descriptor for a model that was hash-enriched from the OpenModelDB
+ * catalogue: it carries no `source_url`, so `getModelSourceInfo` finds
+ * nothing and the page link lives in the civitai payload instead.
+ */
+function getOpenModelDBSourceInfo(model) {
+    const url = model?.civitai?.openmodeldb?.url;
+    if (typeof url !== 'string' || !url) return null;
+    const descriptor = getModelSource('openmodeldb');
+    return descriptor ? { ...descriptor, sourceId: '', url } : null;
+}
+
 const COMMERCIAL_ICON_CONFIG = [
     {
         key: 'image',
@@ -398,7 +410,7 @@ export async function showModelModal(model, modelType) {
 <div class="civitai-view" title="${translate('modals.model.actions.viewOnCivitai', {}, 'View on Civitai')}" data-action="view-civitai" data-filepath="${escapedFilePathAttr}">
     <i class="fas fa-globe"></i> ${translate('modals.model.actions.viewOnCivitaiText', {}, 'View on Civitai')}
 </div>`.trim() : '';
-    const sourceInfo = getModelSourceInfo(modelWithFullData);
+    const sourceInfo = getModelSourceInfo(modelWithFullData) || getOpenModelDBSourceInfo(modelWithFullData);
     const escapedSourceUrl = sourceInfo?.url ? escapeAttribute(sourceInfo.url) : '';
     const isHuggingFaceSource = sourceInfo?.platform === 'huggingface';
     const sourceTitle = sourceInfo ? getModelSourceViewTitle(sourceInfo) : '';

static/js/managers/DownloadManager.js

@@ -18,7 +18,7 @@ import {
     detectModelSourceDownloadUrl,
     getModelSource,
     isExternalModelSource,
-    isValidRepoId,
+    isValidSourceId,
 } from '../utils/modelSourceHelpers.js';
 
 export class DownloadManager {
@@ -534,7 +534,7 @@ export class DownloadManager {
         const sourceInfo = detectModelSourceDownloadUrl(trimmed);
         if (sourceInfo) {
             // Reject path-traversal patterns like "../.." or "user/.."
-            if (!isValidRepoId(sourceInfo.repo)) {
+            if (!isValidSourceId(sourceInfo.platform, sourceInfo.repo)) {
                 return null;
             }
             return {

static/js/managers/SettingsManager.js

@@ -3711,6 +3711,11 @@ export class SettingsManager {
                 enableCivarchiveApiCheckbox.checked = state.global.settings.enable_civarchive_api ?? true;
             }
 
+            const enableOpenmodeldbApiCheckbox = document.getElementById('enableOpenmodeldbApi');
+            if (enableOpenmodeldbApiCheckbox) {
+                enableOpenmodeldbApiCheckbox.checked = state.global.settings.enable_openmodeldb_api ?? true;
+            }
+
             const metadataProviderOrderSelect = document.getElementById('metadataProviderOrder');
             if (metadataProviderOrderSelect) {
                 metadataProviderOrderSelect.value = state.global.settings.metadata_provider_order || 'civitai_archive_sqlite';

static/js/state/index.js

@@ -16,6 +16,7 @@ const DEFAULT_SETTINGS_BASE = Object.freeze({
     show_only_sfw: false,
     enable_metadata_archive_db: false,
     enable_civarchive_api: true,
+    enable_openmodeldb_api: true,
     metadata_provider_order: 'civitai_archive_sqlite',
     proxy_enabled: false,
     proxy_type: 'http',

static/js/utils/modelSourceHelpers.js

@@ -1,5 +1,5 @@
 /**
- * External model source helpers (Hugging Face / ModelScope / TensorArt).
+ * External model source helpers (Hugging Face / ModelScope / TensorArt / OpenModelDB).
  *
  * Mirrors `py/services/model_sources/registry.py` so the frontend and the
  * backend agree on URL recognition, version-group keys, and which sites
@@ -92,6 +92,26 @@ export const MODEL_SOURCES = [
     canonical: (id) => `https://tensor.art/models/${id}`,
     filePage: null,
   },
+  {
+    // Flat catalogue of upscalers: the id IS the published-model identity
+    // (no owner/repo split, no revisions, no per-file page).
+    platform: 'openmodeldb',
+    label: 'OpenModelDB',
+    groupPrefix: 'omdb',
+    groupKey: 'repo',
+    supportsEnrichment: true,
+    supportsDownload: true,
+    defaultRevision: '',
+    defaultSubdir: 'openmodeldb',
+    exampleUrl: 'https://openmodeldb.info/models/4x-UltraSharp',
+    placeholder: 'https://openmodeldb.info/models/4x-UltraSharp',
+    pattern: /^https?:\/\/(?:www\.)?openmodeldb\.info\/models\/([A-Za-z0-9_][A-Za-z0-9_.-]*)/i,
+    filePattern: null,
+    // Flat model ids (no owner/name split).
+    flatId: true,
+    canonical: (id) => `https://openmodeldb.info/models/${id}`,
+    filePage: null,
+  },
 ];
 
 /** Return the source descriptor for a platform id, or null. */
@@ -257,6 +277,18 @@ export function isValidRepoId(repo) {
     .every((part) => part && part !== '.' && part !== '..' && /^[A-Za-z0-9_][\w.-]*$/.test(part));
 }
 
+/**
+ * Source-aware id validation, mirroring `ModelSource.is_valid_source_id`:
+ * `owner/name` for repository sites, a flat token for OpenModelDB.
+ */
+export function isValidSourceId(platform, repo) {
+  const source = getModelSource(platform);
+  if (source?.flatId) {
+    return typeof repo === 'string' && /^[A-Za-z0-9_][A-Za-z0-9_.-]*$/.test(repo);
+  }
+  return isValidRepoId(repo);
+}
+
 /**
  * Recognise a downloadable model-source URL.
  *