Add server, routes, views, CLI, CSS, and integration tests

- Server factory with Fastify plugins (JWT, cookie, multipart, formbody, static)
- Auth middleware: requireAuth preHandler (401 for API, redirect for pages)
- Auth API routes: POST /api/v1/auth/login, POST /api/v1/auth/logout
- File API routes: GET/POST /api/v1/files, DELETE /api/v1/files/:id
- Page routes: /, /login, /logout, /upload, /files, /files/:id/delete, /f/:id, /f/:id/raw
- HTML views: layout, login, upload, file-list, file-view, not-found
- CLI register-user script
- public/style.css dark theme
- Test helpers: createTestApp, loginAs, buildMultipart
- Integration tests for auth API, file API, and page routes (51 tests passing)
- Update CLAUDE.md with red/green TDD and commit instructions

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

CLAUDE.md

@@ -21,7 +21,7 @@ Simple file-sharing platform. TypeScript + Fastify + SQLite.
 ## Code Quality
 
 - Review code after every change. Refactor for readability.
-- Use TDD: write tests first, then implement.
+- Use strict red/green TDD: write the test first, confirm it FAILS (red), then implement until it passes (green).
 - Build and test after every change.
 - Break large functions into smaller ones, extract duplicate code.
 - Search for duplicated code in tests and extract into reusable helpers.