feat(frontend): T44 setup FastAPI static files and templates

- Mount static files on /static endpoint
- Configure Jinja2Templates with directory structure
- Create base template with Pico.css, HTMX, Chart.js
- Create all template subdirectories (auth, dashboard, keys, tokens, profile, components)
- Create initial CSS and JS files
- Add tests for static files and templates configuration

Tests: 12 passing
Coverage: 100% on new configuration code

templates/stats/index.html

@@ -0,0 +1,135 @@
+{% extends "base.html" %}
+
+{% block title %}Statistics - OpenRouter Monitor{% endblock %}
+
+{% block content %}
+<h1>Detailed Statistics</h1>
+
+<!-- Filters -->
+<article>
+    <header>
+        <h3>Filters</h3>
+    </header>
+    <form action="/stats" method="GET" hx-get="/stats" hx-target="#stats-results" hx-push-url="true">
+        <div class="grid">
+            <label for="start_date">
+                Start Date
+                <input type="date" id="start_date" name="start_date" value="{{ filters.start_date }}">
+            </label>
+            
+            <label for="end_date">
+                End Date
+                <input type="date" id="end_date" name="end_date" value="{{ filters.end_date }}">
+            </label>
+            
+            <label for="api_key_id">
+                API Key
+                <select id="api_key_id" name="api_key_id">
+                    <option value="">All Keys</option>
+                    {% for key in api_keys %}
+                    <option value="{{ key.id }}" {% if filters.api_key_id == key.id %}selected{% endif %}>
+                        {{ key.name }}
+                    </option>
+                    {% endfor %}
+                </select>
+            </label>
+            
+            <label for="model">
+                Model
+                <input type="text" id="model" name="model" placeholder="gpt-4" value="{{ filters.model }}">
+            </label>
+        </div>
+        
+        <button type="submit">Apply Filters</button>
+        <a href="/stats/export?{{ query_string }}" role="button" class="secondary">Export CSV</a>
+    </form>
+</article>
+
+<!-- Results -->
+<article id="stats-results">
+    <header>
+        <h3>Usage Details</h3>
+        <p><small>Showing {{ stats|length }} results</small></p>
+    </header>
+    
+    <table class="table">
+        <thead>
+            <tr>
+                <th>Date</th>
+                <th>API Key</th>
+                <th>Model</th>
+                <th>Requests</th>
+                <th>Prompt Tokens</th>
+                <th>Completion Tokens</th>
+                <th>Total Tokens</th>
+                <th>Cost</th>
+            </tr>
+        </thead>
+        <tbody>
+            {% for stat in stats %}
+            <tr>
+                <td>{{ stat.date }}</td>
+                <td>{{ stat.api_key_name }}</td>
+                <td>{{ stat.model }}</td>
+                <td>{{ stat.requests }}</td>
+                <td>{{ stat.prompt_tokens }}</td>
+                <td>{{ stat.completion_tokens }}</td>
+                <td>{{ stat.total_tokens }}</td>
+                <td>${{ stat.cost | round(4) }}</td>
+            </tr>
+            {% else %}
+            <tr>
+                <td colspan="8" style="text-align: center;">No data found for the selected filters.</td>
+            </tr>
+            {% endfor %}
+        </tbody>
+    </table>
+    
+    <!-- Pagination -->
+    {% if total_pages > 1 %}
+    <nav>
+        <ul>
+            {% if page > 1 %}
+            <li>
+                <a href="?page={{ page - 1 }}&{{ query_string }}" class="secondary">&laquo; Previous</a>
+            </li>
+            {% endif %}
+            
+            {% for p in range(1, total_pages + 1) %}
+            <li>
+                {% if p == page %}
+                <strong>{{ p }}</strong>
+                {% else %}
+                <a href="?page={{ p }}&{{ query_string }}">{{ p }}</a>
+                {% endif %}
+            </li>
+            {% endfor %}
+            
+            {% if page < total_pages %}
+            <li>
+                <a href="?page={{ page + 1 }}&{{ query_string }}" class="secondary">Next &raquo;</a>
+            </li>
+            {% endif %}
+        </ul>
+    </nav>
+    {% endif %}
+</article>
+
+<!-- Summary -->
+<article>
+    <header>
+        <h3>Summary</h3>
+    </header>
+    <div class="grid">
+        <div>
+            <strong>Total Requests:</strong> {{ summary.total_requests }}
+        </div>
+        <div>
+            <strong>Total Tokens:</strong> {{ summary.total_tokens }}
+        </div>
+        <div>
+            <strong>Total Cost:</strong> ${{ summary.total_cost | round(2) }}
+        </div>
+    </div>
+</article>
+{% endblock %}