feat: add flexible capability-based RBAC with per-tenant customization

Introduces a capability layer on top of existing roles that controls
feature visibility and access. Capabilities follow an area.feature.action
taxonomy (~35 capabilities) with sensible defaults per role. Tenant admins
can customize via grant/revoke overrides stored in org settings JSONB.

Key changes:
- Add vice_president role to DB schema
- Backend: capability constants, resolution logic, CapabilityGuard (global),
  @RequireCapability decorator on all 16 tenant controllers
- Frontend: permission hooks (useCanEdit, useHasCapability), CapabilityGate
  component, sidebar filtering by capability, all 17 pages migrated from
  useIsReadOnly to capability-based checks
- New admin UI: /settings/permissions matrix page for per-tenant role
  customization with grant/revoke delta model
- GET /organizations/my-capabilities endpoint for capability refresh
- Validation of permissionOverrides in settings updates

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

backend/src/modules/investments/investments.controller.ts

@@ -1,6 +1,7 @@
 import { Controller, Get, Post, Put, Body, Param, UseGuards } from '@nestjs/common';
 import { ApiTags, ApiBearerAuth } from '@nestjs/swagger';
 import { JwtAuthGuard } from '../auth/guards/jwt-auth.guard';
+import { RequireCapability } from '../../common/decorators/capability.decorator';
 import { InvestmentsService } from './investments.service';
 
 @ApiTags('investments')
@@ -11,14 +12,18 @@ export class InvestmentsController {
   constructor(private service: InvestmentsService) {}
 
   @Get()
+  @RequireCapability('planning.investments.view')
   findAll() { return this.service.findAll(); }
 
   @Get(':id')
+  @RequireCapability('planning.investments.view')
   findOne(@Param('id') id: string) { return this.service.findOne(id); }
 
   @Post()
+  @RequireCapability('planning.investments.edit')
   create(@Body() dto: any) { return this.service.create(dto); }
 
   @Put(':id')
+  @RequireCapability('planning.investments.edit')
   update(@Param('id') id: string, @Body() dto: any) { return this.service.update(id, dto); }
 }