feat: add target organization to Add Repository dialog (#202)

* feat: add target organization field to Add Repository dialog

Allow users to specify a destination Gitea organization when adding a
single repository, instead of relying solely on the default mirror
strategy. The field is optional — when left empty, the existing strategy
logic applies as before.

Closes #200

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

* docs: add screenshot of target organization field in Add Repository dialog

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

---------

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

src/pages/api/sync/repository.ts

@@ -20,7 +20,7 @@ export const POST: APIRoute = async ({ request, locals }) => {
     const userId = authResult.userId;
 
     const body: AddRepositoriesApiRequest = await request.json();
-    const { owner, repo, force = false } = body;
+    const { owner, repo, force = false, destinationOrg } = body;
 
     if (!owner || !repo) {
       return new Response(
@@ -122,7 +122,7 @@ export const POST: APIRoute = async ({ request, locals }) => {
       lastMirrored: existingRepo?.lastMirrored ?? null,
       errorMessage: existingRepo?.errorMessage ?? null,
       mirroredLocation: existingRepo?.mirroredLocation ?? "",
-      destinationOrg: existingRepo?.destinationOrg ?? null,
+      destinationOrg: destinationOrg?.trim() || existingRepo?.destinationOrg || null,
       updatedAt: repoData.updated_at
         ? new Date(repoData.updated_at)
         : new Date(),