Add NextSnap PWA with photo gallery viewer and continuous capture

Offline-first photo capture app for Nextcloud with:
- Camera capture with continuous mode (auto-reopens after each photo)
- File browser with fullscreen image gallery, swipe navigation, and rename
- Upload queue with background sync engine
- Admin panel for Nextcloud user management
- Service worker for offline-first caching (v13)

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

app/templates/login.html

@@ -0,0 +1,208 @@
+{% extends "base.html" %}
+
+{% block title %}Login - NextSnap{% endblock %}
+
+{% block content %}
+<div class="container">
+    <div class="login-container">
+        <div class="login-header">
+            <div class="app-icon">📷</div>
+            <h1 class="login-title">NextSnap</h1>
+            <p class="login-subtitle">Offline-first photo capture for Nextcloud</p>
+        </div>
+        
+        <form id="login-form" class="login-form">
+            <div class="form-group">
+                <label for="username">Nextcloud Username</label>
+                <input 
+                    type="text" 
+                    id="username" 
+                    name="username" 
+                    class="form-input" 
+                    placeholder="Enter your username"
+                    autocomplete="username"
+                    autocapitalize="none"
+                    autocorrect="off"
+                    autofocus
+                    required
+                >
+                <span class="field-error" id="username-error"></span>
+            </div>
+            
+            <div class="form-group">
+                <label for="password">Password</label>
+                <input 
+                    type="password" 
+                    id="password" 
+                    name="password" 
+                    class="form-input" 
+                    placeholder="Enter your password"
+                    autocomplete="current-password"
+                    required
+                >
+                <span class="field-error" id="password-error"></span>
+            </div>
+            
+            <div id="error-message" class="error-message hidden"></div>
+            
+            <button type="submit" class="btn btn-primary btn-login" id="login-btn">
+                <span id="login-btn-text">Login</span>
+                <span id="login-btn-loading" class="hidden">
+                    <span class="spinner"></span> Logging in...
+                </span>
+            </button>
+        </form>
+        
+        <div class="login-footer">
+            <p class="help-text">
+                <strong>Tip:</strong> Use your Nextcloud credentials to login
+            </p>
+        </div>
+    </div>
+</div>
+{% endblock %}
+
+{% block extra_css %}
+<style>
+body {
+    background: linear-gradient(135deg, var(--bg-primary) 0%, var(--bg-secondary) 100%);
+}
+
+.login-container {
+    max-width: 400px;
+    margin: 2rem auto;
+    padding: 2rem;
+    background: var(--bg-secondary);
+    border-radius: 16px;
+    box-shadow: 0 4px 6px rgba(0, 0, 0, 0.1);
+}
+
+.login-header {
+    text-align: center;
+    margin-bottom: 2rem;
+}
+
+.app-icon {
+    font-size: 4rem;
+    margin-bottom: 1rem;
+}
+
+.login-title {
+    font-size: 2rem;
+    font-weight: 700;
+    margin-bottom: 0.5rem;
+}
+
+.login-subtitle {
+    color: var(--text-secondary);
+    font-size: 0.9rem;
+}
+
+.login-form {
+    display: flex;
+    flex-direction: column;
+    gap: 1.5rem;
+}
+
+.form-group {
+    display: flex;
+    flex-direction: column;
+    gap: 0.5rem;
+}
+
+.form-group label {
+    font-weight: 600;
+    font-size: 0.9rem;
+}
+
+.form-input {
+    width: 100%;
+    padding: 0.75rem;
+    font-size: 1rem;
+    border: 2px solid var(--bg-tertiary);
+    border-radius: 8px;
+    background: var(--bg-primary);
+    color: var(--text-primary);
+    transition: border-color 0.2s;
+}
+
+.form-input:focus {
+    outline: none;
+    border-color: var(--accent);
+}
+
+.form-input.error {
+    border-color: var(--error);
+}
+
+.field-error {
+    color: var(--error);
+    font-size: 0.85rem;
+    min-height: 1.2rem;
+}
+
+.error-message {
+    padding: 0.75rem;
+    background: var(--error);
+    color: white;
+    border-radius: 8px;
+    font-size: 0.9rem;
+}
+
+.btn-login {
+    margin-top: 0.5rem;
+    position: relative;
+}
+
+.btn-login:disabled {
+    opacity: 0.6;
+    cursor: not-allowed;
+}
+
+.spinner {
+    display: inline-block;
+    width: 14px;
+    height: 14px;
+    border: 2px solid rgba(255, 255, 255, 0.3);
+    border-top-color: white;
+    border-radius: 50%;
+    animation: spin 0.8s linear infinite;
+}
+
+@keyframes spin {
+    to { transform: rotate(360deg); }
+}
+
+.login-footer {
+    margin-top: 2rem;
+    padding-top: 1.5rem;
+    border-top: 1px solid var(--bg-tertiary);
+}
+
+.help-text {
+    text-align: center;
+    color: var(--text-secondary);
+    font-size: 0.85rem;
+}
+
+/* Mobile responsiveness */
+@media (max-width: 480px) {
+    .login-container {
+        margin: 1rem;
+        padding: 1.5rem;
+    }
+    
+    .app-icon {
+        font-size: 3rem;
+    }
+    
+    .login-title {
+        font-size: 1.75rem;
+    }
+}
+</style>
+{% endblock %}
+
+{% block extra_js %}
+<script src="{{ url_for('static', filename='js/auth.js') }}"></script>
+{% endblock %}