feat(core): improve byok editing (#15427)

fix #14287
fix #15359
fix #15424

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit

* **New Features**
* Redesigned workspace AI provider settings with connection testing,
storage options, model selection, capability management, ordering, and
custom endpoints.
* AI chat model choices now adapt to the selected workspace and
conversation route.
  * Added support for image-based AI requests.
* **Bug Fixes**
  * Improved handling of unavailable or outdated model selections.
* App configuration updates now reject overlapping paths and load
deterministically.
* **Tests**
* Expanded coverage for provider models, AI chat scoping, image
requests, and configuration validation.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

packages/backend/server/src/models/config.ts

@@ -9,11 +9,34 @@ export class AppConfigModel extends BaseModel {
   async load(excludedKeys: string[] = []) {
     return this.db.appConfig.findMany({
       where: excludedKeys.length ? { id: { notIn: excludedKeys } } : undefined,
+      orderBy: { id: 'asc' },
     });
   }
 
   @Transactional()
   async save(user: string, updates: Array<{ key: string; value: any }>) {
+    await this.db
+      .$executeRaw`SELECT pg_advisory_xact_lock(hashtextextended(${'app-config-paths'}, 0))`;
+    const existing = await this.db.appConfig.findMany({
+      select: { id: true },
+    });
+    const updateKeys = updates.map(update => update.key);
+    for (const [index, key] of updateKeys.entries()) {
+      const overlappingKey = [
+        ...existing.map(config => config.id),
+        ...updateKeys.slice(0, index),
+      ].find(
+        candidate =>
+          candidate !== key &&
+          (candidate.startsWith(`${key}.`) || key.startsWith(`${candidate}.`))
+      );
+      if (overlappingKey) {
+        throw new Error(
+          `App config paths must not overlap: ${overlappingKey} and ${key}`
+        );
+      }
+    }
+
     return await Promise.allSettled(
       updates.map(async update => {
         return this.db.appConfig.upsert({