feat: implement user authentication and admin management

- Add user management API endpoints for listing and creating users.
- Implement login and logout functionality with rate limiting.
- Create UI components for login form, logout button, and animated elements.
- Add session management with JWT and secure cookie handling.
- Seed initial admin user if no users exist.
- Introduce utility functions for password hashing and user authentication.
- Set up proxy middleware for route protection and security headers.
- Create a JSON file for user data storage.
- Add links configuration for external resources.

frontend/lib/links.ts

@@ -0,0 +1,31 @@
+/**
+ * ─────────────────────────────────────────────────────────────
+ *  LINK CONFIGURATION
+ *  Edit this file to update every link across the entire site.
+ * ─────────────────────────────────────────────────────────────
+ */
+export const LINKS = {
+  // ── GitHub ────────────────────────────────────────────────
+  /** Repository root — used in the nav, footer, and call-to-action buttons */
+  github:             "https://github.com/evan-buss/backerup",
+  /** Releases / changelog page */
+  githubReleases:     "https://github.com/evan-buss/backerup/releases",
+  /** Issue tracker */
+  githubIssues:       "https://github.com/evan-buss/backerup/issues",
+  /** GitHub Discussions forum */
+  githubDiscussions:  "https://github.com/evan-buss/backerup/discussions",
+  /** CONTRIBUTING.md guide */
+  githubContributing: "https://github.com/evan-buss/backerup/blob/main/CONTRIBUTING.md",
+
+  // ── Documentation ─────────────────────────────────────────
+  /** Primary documentation URL (separate from GitHub if hosted elsewhere) */
+  docs:               "https://github.com/evan-buss/backerup",
+
+  // ── Docker ────────────────────────────────────────────────
+  /** Full Docker image reference shown in install snippets */
+  dockerImage:        "ghcr.io/evan-buss/backerup:latest",
+  /** Default UI port the container exposes */
+  uiPort:             "8080",
+} as const;
+
+export type Links = typeof LINKS;