refactor(frontend): convert Create Deployment modal to a dedicated page

[jeffmccune]

Parent Issue

Part of #394

Goal

Replace the Create Deployment modal (currently inline in the deployments index page) with a dedicated page at /projects/$projectName/deployments/new. The modal has too many form fields (8+) for a dialog, and users lose their work by accidentally clicking outside.

Acceptance Criteria

• New route at /_authenticated/projects/$projectName/deployments/new renders a Create Deployment page
• Page contains all existing form fields: Display Name, Name (slug), Description, Template select, Image, Tag, Command (StringListInput), Args (StringListInput), Environment Variables (EnvVarEditor)
• "Create Deployment" button on deployments list page navigates to the new page (not a modal)
• Empty state on deployments list page also links to the new page
• When no templates exist, show a link to /projects/$projectName/templates/new instead of opening a sub-modal
• On successful creation, navigates to the deployment detail page (/projects/$projectName/deployments/$deploymentName)
• Form validation preserved (name, template, image, tag required)
• Unit tests for the new page component with mocked query hooks
• Tests pass: make test

Implementation Notes

Files to create

• frontend/src/routes/_authenticated/projects/$projectName/deployments/new.tsx — the new Create Deployment page route
• frontend/src/routes/_authenticated/projects/$projectName/deployments/-new.test.tsx — unit tests

Files to modify

• frontend/src/routes/_authenticated/projects/$projectName/deployments/index.tsx — remove inline modal code (~120 lines), replace "Create Deployment" button with <Link to="new"> navigation

Key patterns to follow

• Use createFileRoute('/_authenticated/projects/$projectName/deployments/new') for the route definition
• Use useNavigate() to redirect after successful creation
• Use useCreateDeployment from @/queries/deployments and useListDeploymentTemplates from @/queries/deployment-templates
• Reuse existing components: StringListInput, EnvVarEditor, filterEnvVars
• When no templates exist, render a link: "No templates available. Create a template first."
• The page layout gives much more room for the env var editor and command/args fields

Testing approach

• Mock @/queries/deployments and @/queries/deployment-templates with vi.mock() and vi.fn()
• Test form rendering, validation (required fields), submission with all fields, template selection
• Test the "no templates" state shows a link to create templates page
• Test role-based access (OWNER/EDITOR can create, VIEWER cannot see the page or button)
• Follow patterns from the existing -index.test.tsx file

Dependencies

Depends on #395 (Create Template page) — the "no templates" link targets the new template creation page.

[jeffmccune]

Working on this issue.

• Agent path: /Users/jeff/workspace/holos-run/holos-console/.claude/worktrees/agent-aca14464
• Hostname: tr-mac.lan
• Branch: feat/396-convert-create-deployment-modal-to-dedicated-page