feat(studio-local): functions management api - function details (#42322)

Functions page on self-hosted differs from Platform Adds the possibility to see function details page in Self-Host version.

## Summary by CodeRabbit

* **New Features**
* Edge function detail lookup added for self‑hosted deployments (new
retrieval endpoint & store method).
  * Consistent navigation to function pages from the functions list.

* **Improvements**
  * UI tabs, download, and test controls adapt to deployment type.
* Region, JWT verification, local development, and delete controls shown
only on the platform.
* Edit/save/delete controls enable/disable correctly based on deployment
and permissions.
  * Function details load reliably across deployments.

apps/studio/lib/api/self-hosted/functions/fileSystemStore.ts

@@ -18,6 +18,17 @@ export class FileSystemFunctionsArtifactStore {
 
     return functionsArtifacts.filter((f) => f !== undefined)
   }
+
+  async getFunctionBySlug(slug: string): Promise<FunctionArtifact | undefined> {
+    const dirEntries = await readdir(this.folderPath, { withFileTypes: true })
+
+    const functionFolder = dirEntries.find(
+      (dir) => dir.isDirectory() && dir.name !== 'main' && dir.name === slug
+    )
+    if (!functionFolder) return
+
+    return parseFolderToFunctionArtifact(functionFolder)
+  }
 }
 
 async function parseFolderToFunctionArtifact(