feat: implement 4 project type flows with unique AI experiences

- New multi-step CreateProjectFlow replaces 2-step modal with TypeSelector
  and 4 setup components (Fresh Idea, Chat Import, Code Import, Migrate)
- overview/page.tsx routes to unique main component per creationMode
- FreshIdeaMain: wraps AtlasChat with post-discovery decision banner
  (Generate PRD vs Plan MVP Test)
- ChatImportMain: 3-stage flow (intake → extracting → review) with
  editable insight buckets (decisions, ideas, questions, architecture, users)
- CodeImportMain: 4-stage flow (input → cloning → mapping → surfaces)
  with architecture map and surface selection
- MigrateMain: 5-stage flow with audit, review, planning, and migration
  plan doc with checkbox-tracked tasks and non-destructive warning banner
- New API routes: analyze-chats, analyze-repo, analysis-status,
  generate-migration-plan (all using Gemini)
- ProjectShell: accepts creationMode prop, filters/renames tabs per type
  (code-import hides PRD, migration hides PRD/Grow/Insights, renames Atlas tab)
- Right panel adapts content based on creationMode

Made-with: Cursor

app/[workspace]/project/[projectId]/layout.tsx

@@ -11,6 +11,7 @@ interface ProjectData {
   createdAt?: string;
   updatedAt?: string;
   featureCount?: number;
+  creationMode?: "fresh" | "chat-import" | "code-import" | "migration";
 }
 
 async function getProjectData(projectId: string): Promise<ProjectData> {
@@ -31,6 +32,7 @@ async function getProjectData(projectId: string): Promise<ProjectData> {
         createdAt: created_at,
         updatedAt: updated_at,
         featureCount: Array.isArray(data?.features) ? data.features.length : (data?.featureCount ?? 0),
+        creationMode: data?.creationMode ?? "fresh",
       };
     }
   } catch (error) {
@@ -62,6 +64,7 @@ export default async function ProjectLayout({
       createdAt={project.createdAt}
       updatedAt={project.updatedAt}
       featureCount={project.featureCount}
+      creationMode={project.creationMode}
     >
       {children}
     </ProjectShell>