schema: add Idea + IdeaLog models, extend ClaudeJob/Question for ideas (M12 T-491)

- new enums IdeaStatus, ClaudeJobKind, IdeaLogType
- new models Idea (with @@unique([user_id, code]) + pbi_id @unique) and IdeaLog
- User.idea_code_counter Int @default(0) for IDEA-{nnn} code generation
- ClaudeJob.task_id nullable; new idea_id + kind fields + index
- ClaudeQuestion.story_id nullable; new idea_id field + index
- existing call sites narrowed to story-questions / task-jobs (idea-paths come in T-502+)
- includes the M12 plan doc copied from /Users/janpetervisser/.claude/plans

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

app/api/realtime/notifications/route.ts

@@ -132,6 +132,7 @@ export async function GET(request: NextRequest) {
           status: 'open',
           expires_at: { gt: new Date() },
           product_id: { in: products.map((p) => p.id) },
+          story_id: { not: null },
         },
         orderBy: { created_at: 'desc' },
         take: 100,
@@ -150,7 +151,9 @@ export async function GET(request: NextRequest) {
 
       enqueue(
         `event: state\ndata: ${JSON.stringify({
-          questions: openQuestions.map((q) => ({
+          questions: openQuestions.flatMap((q) => {
+            if (!q.story || q.story_id === null) return []
+            return [{
             id: q.id,
             product_id: q.product_id,
             story_id: q.story_id,
@@ -162,7 +165,8 @@ export async function GET(request: NextRequest) {
             options: q.options,
             created_at: q.created_at.toISOString(),
             expires_at: q.expires_at.toISOString(),
-          })),
+            }]
+          }),
         })}\n\n`,
       )