Refactor admin pages to use shared head and navigation components

- Created `admin-head.php` for consistent <head> markup across admin pages.
- Created `admin-nav.php` for shared navigation bar, reducing duplication.
- Updated all admin pages (account, hours, index, login, menu, users) to utilize the new components.
- Added security headers to `auth.php` and `index.php` for improved security.
- Introduced `security-headers.php` to manage security headers across the application.
- Moved inline styles from admin pages to SCSS files to comply with Content Security Policy (CSP).
- Normalized file permissions during build process to prevent permission issues on deployment.

styles.css

@@ -1933,9 +1933,65 @@ footer a.email:hover {
 }
 
 .menu-page-content {
+  padding-top: 0;
   padding-bottom: 5.5rem;
 }
 
+/* Formerly inline style="" attributes on menu.php — moved here so the
+   CSP can forbid inline styles. */
+.menu-hero {
+  text-align: center;
+}
+
+.menu-hero-title {
+  font-size: clamp(2.4rem, 5vw, 3.8rem);
+  color: var(--gold-bright);
+  margin-top: 0.5rem;
+}
+
+.menu-hero-rule {
+  margin-top: 1.5rem;
+  margin-bottom: 1.5rem;
+}
+
+.menu-hero-intro {
+  max-width: 52ch;
+  margin: 0 auto;
+  font-size: 1.05rem;
+}
+
+.menu-page-container {
+  max-width: 62rem;
+}
+
+.menu-grid-flush {
+  margin-top: 0;
+}
+
+.menu-empty {
+  text-align: center;
+  padding: 3rem 1.5rem;
+}
+
+.menu-disclaimer {
+  margin-top: 3.5rem;
+  text-align: center;
+  padding-top: 2rem;
+  border-top: 1px solid var(--rule);
+}
+
+.menu-disclaimer-text {
+  font-size: 0.8rem;
+  line-height: 1.6;
+  max-width: 68ch;
+  margin: 0 auto;
+}
+
+.menu-disclaimer-ctas {
+  margin-top: 2rem;
+  justify-content: center;
+}
+
 /* ---------- admin / management styles ---------- */
 .admin-login-body {
   min-height: 100vh;
@@ -2196,6 +2252,45 @@ footer a.email:hover {
     grid-template-columns: 1fr;
   }
 }
+/* Formerly inline style="" attributes on admin/hours.php. */
+.hours-note {
+  margin-top: 1.25rem;
+}
+
+.hours-preview-intro {
+  margin-bottom: 1.25rem;
+}
+
+/* ---------- admin: announcements ---------- */
+/* Formerly inline style="" attributes on admin/index.php — moved here so
+   the CSP can forbid inline styles. */
+.ann-summary {
+  font-size: 0.82rem;
+  margin-top: 0.2rem;
+  max-width: 32ch;
+  white-space: nowrap;
+  overflow: hidden;
+  text-overflow: ellipsis;
+}
+
+.ann-schedule {
+  font-size: 0.8rem;
+  color: var(--ink-muted);
+}
+
+.ann-placements {
+  font-size: 0.82rem;
+  color: var(--ink-muted);
+}
+
+.ann-field-hint {
+  font-size: 0.78rem;
+}
+
+.inline-form {
+  display: inline;
+}
+
 /* ---------- admin: my account ---------- */
 /* One panel, fields in the shared two-column .form-grid (which already
    stacks below 47.5em). Capped so the fields don't stretch across the