feat(ui): add responsive CSS for mobile accessibility

- Add mobile-first responsive CSS to base.html
- Wrap all tables in .table-container for horizontal scrolling on mobile
- Add breakpoints for phones (576px), tablets (768px), desktops (992px, 1200px)
- Improve mobile navigation (vertical stack) and form layouts (full-width)
- Add print styles for clean printing
- Update project_management.html editor for mobile
- Document all changes in docs/RESPONSIVE_CSS.md

No backend or JavaScript changes - pure CSS solution.
For 5 internal technical users, this is simpler and more appropriate than
HTMX or SPA approaches. Solves mobile accessibility issue with minimal changes.

templates/base.html

@@ -123,7 +123,178 @@
         textarea {
             height: 100px;
         }
-    </style>
+
+        /* ============================================
+           RESPONSIVE DESIGN - Mobile First
+           Added for internal technical staff mobile access
+           ============================================ */
+
+        /* Mobile-first base styles */
+        .container {
+            max-width: 100%;
+            padding: 1rem;
+            margin: 0 auto;
+        }
+
+        /* Navigation - stack vertically on mobile */
+        .nav {
+            display: flex;
+            flex-direction: column;
+            gap: 0.5rem;
+            margin-bottom: 1rem;
+        }
+        .nav a {
+            padding: 0.75rem 1rem;
+            text-align: center;
+            white-space: nowrap;
+        }
+
+        /* Tables - responsive with horizontal scroll */
+        .table-container {
+            overflow-x: auto;
+            -webkit-overflow-scrolling: touch;
+            margin-top: 1rem;
+        }
+        table {
+            min-width: 600px;
+            width: 100%;
+        }
+        th, td {
+            padding: 0.75rem;
+            white-space: nowrap;
+        }
+
+        /* Forms - full width on mobile */
+        form {
+            max-width: 100%;
+        }
+        input[type="text"],
+        input[type="email"],
+        input[type="password"],
+        input[type="number"],
+        textarea,
+        select {
+            width: 100%;
+            padding: 0.75rem;
+            margin-bottom: 1rem;
+            box-sizing: border-box;
+        }
+
+        /* Buttons - full width on mobile */
+        .btn {
+            padding: 0.75rem 1.5rem;
+            width: 100%;
+            margin-bottom: 0.5rem;
+            display: block;
+        }
+        .btn:last-child {
+            margin-bottom: 0;
+        }
+
+        /* Cards for mobile display */
+        .tablet-card,
+        .user-card,
+        .loan-card {
+            background: white;
+            border-radius: 8px;
+            padding: 1rem;
+            margin-bottom: 1rem;
+            box-shadow: 0 2px 4px rgba(0,0,0,0.1);
+            border: 1px solid #e0e0e0;
+        }
+
+        /* Flash messages */
+        .flash-message {
+            padding: 1rem;
+            margin-bottom: 1rem;
+            border-radius: 4px;
+        }
+
+        /* Section spacing */
+        .section {
+            margin-bottom: 1.5rem;
+        }
+
+        /* ============================================
+           BREAKPOINTS - Tablet and Desktop
+           ============================================ */
+
+        /* Small devices (landscape phones, 576px and up) */
+        @media (min-width: 576px) {
+            .container {
+                max-width: 540px;
+            }
+            .nav {
+                flex-direction: row;
+                flex-wrap: wrap;
+            }
+            .nav a {
+                flex: 1 1 auto;
+                min-width: 120px;
+            }
+            .btn {
+                width: auto;
+                display: inline-block;
+                margin-bottom: 0;
+                margin-right: 0.5rem;
+            }
+            .btn:last-child {
+                margin-right: 0;
+            }
+        }
+
+        /* Medium devices (tablets, 768px and up) */
+        @media (min-width: 768px) {
+            body {
+                padding: 1rem;
+            }
+            .container {
+                max-width: 720px;
+                padding: 1.5rem;
+            }
+            table {
+                min-width: auto;
+            }
+            .table-container {
+                overflow-x: visible;
+            }
+        }
+
+        /* Large devices (desktops, 992px and up) */
+        @media (min-width: 992px) {
+            .container {
+                max-width: 960px;
+            }
+            .nav {
+                flex-wrap: nowrap;
+            }
+        }
+
+        /* Extra large devices (large desktops, 1200px and up) */
+        @media (min-width: 1200px) {
+            .container {
+                max-width: 1140px;
+            }
+        }
+
+        /* Print styles */
+        @media print {
+            .nav,
+            .btn,
+            .flash-message {
+                display: none !important;
+            }
+            body {
+                background: white;
+                padding: 0;
+            }
+            .container {
+                box-shadow: none;
+                border: none;
+                max-width: 100%;
+                padding: 0;
+            }
+        }
 </head>
 <body>
     <div class="container">