feat: add server-side session filtering with input bytes and human score

Replace client-side session table filtering with server-side filtering
via a new /fragments/recent-sessions htmx endpoint. Add InputBytes column
to session tables, Human score > 0 checkbox filter, and Sort by Input
Bytes option to help identify sessions with actual shell interaction.

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

internal/web/templates/fragments/recent_sessions.html

@@ -0,0 +1,17 @@
+{{define "recent_sessions"}}
+{{range .}}
+<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>{{formatBytes .InputBytes}}</td>
+    <td>{{formatTime .ConnectedAt}}</td>
+    <td>{{if .DisconnectedAt}}{{formatTime (derefTime .DisconnectedAt)}}{{else}}<mark>active</mark>{{end}}</td>
+</tr>
+{{else}}
+<tr><td colspan="9">No sessions</td></tr>
+{{end}}
+{{end}}