feat(repo): add project-level review prompt with UI redesign

- Add database migration and repository for project review prompts
- Add API endpoint for setting project-level prompts
- Integrate project prompts into Agent and Codex review flows
- Redesign repository management UI with dialog-based prompt editor
- Replace flat buttons with Switch for webhook toggle and dedicated prompt button
- Add Dialog and DropdownMenu UI components from Radix UI
- Add comprehensive tests for wiring and interactions

src/utils/global-prompt.ts

@@ -11,14 +11,32 @@ export function withGlobalPrompt(systemContent: string, globalPrompt: string | u
   return `${systemContent}\n\n${globalPrompt}`;
 }
 
+export function mergeReviewPrompts(
+  globalPrompt: string | undefined,
+  projectPrompt: string | undefined
+): string | undefined {
+  const normalized = [globalPrompt, projectPrompt]
+    .map((item) => item?.trim())
+    .filter((item): item is string => !!item && item.length > 0);
+
+  if (normalized.length === 0) {
+    return undefined;
+  }
+
+  return normalized.join('\n\n');
+}
+
 export function withCoreGlobalPrompt(
   systemContent: string,
   globalPrompt: string | undefined,
-  maxChars = 240
+  maxChars?: number
 ): string {
   if (!globalPrompt || globalPrompt.trim() === '') {
     return systemContent;
   }
-  const compact = globalPrompt.trim().slice(0, maxChars);
+
+  const normalized = globalPrompt.trim();
+  const compact =
+    typeof maxChars === 'number' && maxChars > 0 ? normalized.slice(0, maxChars) : normalized;
   return `${systemContent}\n\n${compact}`;
 }