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/invoices/invoices.controller.ts

@@ -1,6 +1,7 @@
 import { Controller, Get, Post, Body, Param, UseGuards, Request } 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 { InvoicesService } from './invoices.service';
 
 @ApiTags('invoices')
@@ -11,22 +12,27 @@ export class InvoicesController {
   constructor(private invoicesService: InvoicesService) {}
 
   @Get()
+  @RequireCapability('transactions.view')
   findAll() { return this.invoicesService.findAll(); }
 
   @Get(':id')
+  @RequireCapability('transactions.view')
   findOne(@Param('id') id: string) { return this.invoicesService.findOne(id); }
 
   @Post('generate-preview')
+  @RequireCapability('transactions.edit')
   generatePreview(@Body() dto: { month: number; year: number }) {
     return this.invoicesService.generatePreview(dto);
   }
 
   @Post('generate-bulk')
+  @RequireCapability('transactions.edit')
   generateBulk(@Body() dto: { month: number; year: number }, @Request() req: any) {
     return this.invoicesService.generateBulk(dto, req.user.sub);
   }
 
   @Post('apply-late-fees')
+  @RequireCapability('transactions.edit')
   applyLateFees(@Body() dto: { grace_period_days: number; late_fee_amount: number }, @Request() req: any) {
     return this.invoicesService.applyLateFees(dto, req.user.sub);
   }