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/web.go

@@ -40,9 +40,13 @@ func NewServer(store storage.Store, logger *slog.Logger, metricsHandler http.Han
 	s.mux.Handle("GET /static/", http.FileServerFS(staticFS))
 	s.mux.HandleFunc("GET /sessions/{id}", s.handleSessionDetail)
 	s.mux.HandleFunc("GET /api/sessions/{id}/events", s.handleAPISessionEvents)
+	s.mux.HandleFunc("GET /api/charts/attempts-over-time", s.handleAPIAttemptsOverTime)
+	s.mux.HandleFunc("GET /api/charts/hourly-pattern", s.handleAPIHourlyPattern)
+	s.mux.HandleFunc("GET /api/charts/country-stats", s.handleAPICountryStats)
 	s.mux.HandleFunc("GET /", s.handleDashboard)
 	s.mux.HandleFunc("GET /fragments/stats", s.handleFragmentStats)
 	s.mux.HandleFunc("GET /fragments/active-sessions", s.handleFragmentActiveSessions)
+	s.mux.HandleFunc("GET /fragments/dashboard-content", s.handleFragmentDashboardContent)
 
 	if metricsHandler != nil {
 		h := metricsHandler