- Add OrganizationBudgetAlertSettings model with threshold validation
- Add BudgetAlertSettings property to Organization model
- Add ProjectIngestLimit model with Fixed and Percentage types
- Add IngestLimit property to Project model
- Create UpdateOrganization DTO for organization updates
- Add BudgetAlertSettings to ViewOrganization
- Add IngestLimit, EffectiveIngestLimit, IsSmartThrottled,
  SmartThrottleSampleRate to ViewProject
- Update OrganizationController to use UpdateOrganization
- Update Mapperly mappers for new properties

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

- Add OrganizationBudgetAlert and ProjectSmartThrottleApplied messages
- Add work items and handlers for budget alerts and smart throttle
- Add CheckBudgetAlertThresholdsAsync to UsageService for threshold-based
  email alerts with per-billing-period deduplication
- Add GetEventIngestAllowanceAsync for project-specific budget enforcement
- Add GetSmartThrottleRateAsync for fair-share-based sampling
- Integrate smart throttling and project budget limits into EventPostsJob
- Add IMailer methods and Mailer implementations for budget alert and
  throttle notification emails
- Add HTML email templates for both notification types
- Register startup actions and work item handlers in bootstrappers
- Update NullMailer and CountingMailer test doubles

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Wire up EffectiveIngestLimit, IsSmartThrottled, and SmartThrottleSampleRate
in ProjectController.AfterResultMapAsync using UsageService methods.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Regenerate openapi.json to include UpdateOrganization, ProjectIngestLimit,
OrganizationBudgetAlertSettings, and updated ViewProject/ViewOrganization
schemas.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Bug fixes:
- Wrap CheckBudgetAlertThresholdsAsync in try/catch so budget alert
  failures never break event ingestion
- Use Math.Ceiling (not floor cast) for threshold event count and
  percentage project cap calculations
- Add RecordSmartThrottleAsync to publish deduped ProjectSmartThrottleApplied
  notification (once per billing period per project)
- Remove events.Count > 1 guard so single-event posts go through smart throttle
- Fix IsOrganizationNameAvailableInternalAsync to accept excludeOrganizationId
  so PATCH with current name + budget_alert_settings doesn't fail as duplicate
- Update OpenAPI baseline: budget_alert_settings and ingest_limit use proper
  $ref instead of untyped object schemas
- Fix CanRunJob_WhenSmartThrottleApplied test: org needs MaxEventsPerMonth
  set to a finite value and a second project for projectCount > 1 condition

Test coverage:
- UsageServiceTests: 36 new tests covering GetEventIngestAllowanceAsync,
  CheckBudgetAlertThresholdsAsync, GetSmartThrottleRateAsync, percentage
  limit ceiling, and budget alert edge cases
- ProjectControllerTests: ingest limit CRUD, validation, effective limit
  display, and smart throttle status
- EventPostJobTests: project-over-limit blocking and smart throttle
  discard with regression assertions
- OrganizationControllerTests: PATCH with same name + budget_alert_settings
  must not reject as duplicate name

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Add precondition assertion to verify smart throttle is active before running
the job. Without warming the project-count cache first, the ES count query
for GetOrganizationProjectCountAsync may return stale results causing the
throttle to not fire. The pre-assertion also improves test documentation.

Also improve assertion error messages with diagnostic detail.

BLOCKER 1 (frontend): addThreshold() accepted val=100 but backend rejects
threshold >= 100 (valid range is 1-99). Fixed input max attribute and
validation error message in org manage page.

BLOCKER 2 (backend): non-atomic GetAsync+SetAsync for alertSentKey allowed
concurrent workers to both see key absent and both publish duplicate alerts.
Replaced with IncrementAsync (atomic); only the worker whose increment
returns 1 (first writer wins) sends the OrganizationBudgetAlert message.

Tests: adds regression test
CheckBudgetAlertThresholdsAsync_ConcurrentCalls_PublishesAlertExactlyOnce
which fires 5 concurrent IncrementTotalAsync calls and asserts exactly
1 alert is published.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>