feat: add charts, world map, and filters to web dashboard

Add Chart.js line/bar charts for attack trends (attempts over time,
hourly pattern), an SVG world map choropleth colored by attack origin
country, and a collapsible filter form (date range, IP, country,
username) that narrows both charts and top-N tables.

New store methods: GetAttemptsOverTime, GetHourlyPattern, GetCountryStats,
and filtered variants of dashboard stats/top-N queries. New JSON API
endpoints at /api/charts/* and an htmx fragment at
/fragments/dashboard-content for filtered table updates.

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

internal/web/templates/dashboard.html

@@ -3,6 +3,94 @@
     {{template "stats" .Stats}}
 </section>
 
+<details>
+    <summary>Filters</summary>
+    <form id="filter-form">
+        <div class="grid">
+            <label>Since <input type="date" name="since"></label>
+            <label>Until <input type="date" name="until"></label>
+            <label>IP <input type="text" name="ip" placeholder="10.0.0.1"></label>
+            <label>Country <input type="text" name="country" placeholder="CN" maxlength="2"></label>
+            <label>Username <input type="text" name="username" placeholder="root"></label>
+        </div>
+        <button type="submit">Apply</button>
+        <button type="button" class="secondary" onclick="clearFilters()">Clear</button>
+    </form>
+</details>
+
+<section>
+    <h3>Attack Trends</h3>
+    <div class="grid">
+        <article>
+            <header>Attempts Over Time</header>
+            <canvas id="chart-attempts"></canvas>
+        </article>
+        <article>
+            <header>Hourly Pattern (UTC)</header>
+            <canvas id="chart-hourly"></canvas>
+        </article>
+    </div>
+</section>
+
+<section>
+    <h3>Attack Origins</h3>
+    <article>
+        <div id="world-map"></div>
+    </article>
+</section>
+
+<div id="dashboard-content">
+    {{template "dashboard_content" .}}
+</div>
+
+<section>
+    <h3>Active Sessions</h3>
+    <div id="active-sessions" hx-get="/fragments/active-sessions" hx-trigger="every 10s" hx-swap="innerHTML">
+        {{template "active_sessions" .ActiveSessions}}
+    </div>
+</section>
+
+<section>
+    <h3>Recent Sessions</h3>
+    <table id="recent-sessions-table">
+        <thead>
+            <tr>
+                <th>ID</th>
+                <th>IP</th>
+                <th>Country</th>
+                <th>Username</th>
+                <th>Type</th>
+                <th>Score</th>
+                <th>Connected</th>
+                <th>Disconnected</th>
+            </tr>
+        </thead>
+        <tbody>
+            {{range .RecentSessions}}
+            <tr>
+                <td><a href="/sessions/{{.ID}}"><code>{{truncateID .ID}}</code></a>{{if gt .EventCount 0}} <mark>replay</mark>{{end}}</td>
+                <td>{{.IP}}</td>
+                <td>{{.Country}}</td>
+                <td>{{.Username}}</td>
+                <td>{{if .ExecCommand}}<mark>exec</mark>{{else}}{{.ShellName}}{{end}}</td>
+                <td>{{if .HumanScore}}{{if gt (derefFloat .HumanScore) 0.6}}<mark>{{formatScore .HumanScore}}</mark>{{else}}{{formatScore .HumanScore}}{{end}}{{else}}-{{end}}</td>
+                <td>{{formatTime .ConnectedAt}}</td>
+                <td>{{if .DisconnectedAt}}{{formatTime (derefTime .DisconnectedAt)}}{{else}}<mark>active</mark>{{end}}</td>
+            </tr>
+            {{else}}
+            <tr><td colspan="8">No sessions</td></tr>
+            {{end}}
+        </tbody>
+    </table>
+</section>
+{{end}}
+
+{{define "scripts"}}
+<script src="/static/chart.min.js"></script>
+<script src="/static/dashboard.js"></script>
+{{end}}
+
+{{define "dashboard_content"}}
 <section>
     <h3>Top Credentials & IPs</h3>
     <div class="top-grid">
@@ -83,45 +171,4 @@
         </article>
     </div>
 </section>
-
-<section>
-    <h3>Active Sessions</h3>
-    <div id="active-sessions" hx-get="/fragments/active-sessions" hx-trigger="every 10s" hx-swap="innerHTML">
-        {{template "active_sessions" .ActiveSessions}}
-    </div>
-</section>
-
-<section>
-    <h3>Recent Sessions</h3>
-    <table>
-        <thead>
-            <tr>
-                <th>ID</th>
-                <th>IP</th>
-                <th>Country</th>
-                <th>Username</th>
-                <th>Type</th>
-                <th>Score</th>
-                <th>Connected</th>
-                <th>Disconnected</th>
-            </tr>
-        </thead>
-        <tbody>
-            {{range .RecentSessions}}
-            <tr>
-                <td><a href="/sessions/{{.ID}}"><code>{{truncateID .ID}}</code></a>{{if gt .EventCount 0}} <mark>replay</mark>{{end}}</td>
-                <td>{{.IP}}</td>
-                <td>{{.Country}}</td>
-                <td>{{.Username}}</td>
-                <td>{{if .ExecCommand}}<mark>exec</mark>{{else}}{{.ShellName}}{{end}}</td>
-                <td>{{if .HumanScore}}{{if gt (derefFloat .HumanScore) 0.6}}<mark>{{formatScore .HumanScore}}</mark>{{else}}{{formatScore .HumanScore}}{{end}}{{else}}-{{end}}</td>
-                <td>{{formatTime .ConnectedAt}}</td>
-                <td>{{if .DisconnectedAt}}{{formatTime (derefTime .DisconnectedAt)}}{{else}}<mark>active</mark>{{end}}</td>
-            </tr>
-            {{else}}
-            <tr><td colspan="8">No sessions</td></tr>
-            {{end}}
-        </tbody>
-    </table>
-</section>
 {{end}}