feat: implement CMS for content management (WEB-02/03/04/06)

Introduces Filament management for site settings, services, portfolio cases, and testimonials with admin-only policies, validated media uploads, and deterministic seeding. Includes comprehensive design and task documentation for the implementation.

Co-authored-by: Cursor <cursoragent@cursor.com>

openspec/changes/archive/2026-07-29-build-content-cms/specs/service-catalog/spec.md

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+## ADDED Requirements
+
+### Requirement: Services are managed in Filament with publication control
+
+The system SHALL allow admins to create, update, and delete services (SPEC WEB-02). Each service MUST have title, unique slug, summary, description, optional cover image with alt text, sort order, featured flag, and `published_at`.
+
+#### Scenario: Unpublished service is not publicly visible
+
+- **WHEN** a service has `published_at` null
+- **THEN** the `published()` scope MUST exclude it from public queries
+
+#### Scenario: Published service is queryable
+
+- **WHEN** an admin sets `published_at` on a service with required fields
+- **THEN** the service MUST be included in the `published()` scope
+
+#### Scenario: Slug uniqueness is enforced
+
+- **WHEN** an admin attempts to save two services with the same slug
+- **THEN** validation or database constraint MUST reject the duplicate
+
+#### Scenario: Assistant cannot manage services
+
+- **WHEN** an assistant attempts to access the services Resource
+- **THEN** access MUST be denied with HTTP 403
+
+#### Scenario: Delete requires confirmation
+
+- **WHEN** an admin deletes a service in Filament
+- **THEN** the UI MUST require explicit confirmation before deletion