feat: add ideation feature with per-tenant toggle

Adds idea submission capability gated by a per-tenant feature flag.
Super admins can enable/disable ideation for specific tenants via the
admin tenant detail drawer. Users see a lightbulb icon in the header
when enabled, opening a modal to submit ideas (title + description).
Ideas are stored in shared schema for cross-tenant backlog querying.

- Database: shared.ideas table (018-ideas.sql migration)
- Backend: Ideas NestJS module (entity, service, controller)
- Admin API: GET /admin/ideas, PUT /admin/ideas/:id/status,
  PUT /admin/organizations/:id/settings
- Frontend: IdeaModal component, lightbulb ActionIcon in header
- Admin UI: Feature Toggles card with ideation Switch in drawer

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

backend/src/modules/ideas/ideas.controller.ts

@@ -0,0 +1,27 @@
+import { Controller, Get, Post, Body, Req, UseGuards } from '@nestjs/common';
+import { ApiTags, ApiBearerAuth } from '@nestjs/swagger';
+import { JwtAuthGuard } from '../auth/guards/jwt-auth.guard';
+import { IdeasService } from './ideas.service';
+import { CreateIdeaDto } from './dto/create-idea.dto';
+
+@ApiTags('ideas')
+@Controller('ideas')
+@ApiBearerAuth()
+@UseGuards(JwtAuthGuard)
+export class IdeasController {
+  constructor(private ideasService: IdeasService) {}
+
+  @Post()
+  async create(@Req() req: any, @Body() dto: CreateIdeaDto) {
+    const orgId = req.user.orgId;
+    const userId = req.user.userId || req.user.sub;
+    const idea = await this.ideasService.create(orgId, userId, dto);
+    return { success: true, idea };
+  }
+
+  @Get()
+  async findByOrg(@Req() req: any) {
+    const orgId = req.user.orgId;
+    return this.ideasService.findByOrg(orgId);
+  }
+}