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/storage/store.go

@@ -56,6 +56,33 @@ type DashboardStats struct {
 	ActiveSessions int64
 }
 
+// TimeSeriesPoint represents a single data point in a time series.
+type TimeSeriesPoint struct {
+	Timestamp time.Time
+	Count     int64
+}
+
+// HourlyCount represents the total attempts for a given hour of day.
+type HourlyCount struct {
+	Hour  int // 0-23
+	Count int64
+}
+
+// CountryCount represents the total attempts from a given country.
+type CountryCount struct {
+	Country string
+	Count   int64
+}
+
+// DashboardFilter contains optional filters for dashboard queries.
+type DashboardFilter struct {
+	Since    *time.Time
+	Until    *time.Time
+	IP       string
+	Country  string
+	Username string
+}
+
 // TopEntry represents a value and its count for top-N queries.
 type TopEntry struct {
 	Value   string
@@ -127,6 +154,30 @@ type Store interface {
 	// sessions left over from a previous unclean shutdown.
 	CloseActiveSessions(ctx context.Context, disconnectedAt time.Time) (int64, error)
 
+	// GetAttemptsOverTime returns daily attempt counts for the last N days.
+	GetAttemptsOverTime(ctx context.Context, days int, since, until *time.Time) ([]TimeSeriesPoint, error)
+
+	// GetHourlyPattern returns total attempts grouped by hour of day (0-23).
+	GetHourlyPattern(ctx context.Context, since, until *time.Time) ([]HourlyCount, error)
+
+	// GetCountryStats returns total attempts per country, ordered by count DESC.
+	GetCountryStats(ctx context.Context) ([]CountryCount, error)
+
+	// GetFilteredDashboardStats returns aggregate counts with optional filters applied.
+	GetFilteredDashboardStats(ctx context.Context, f DashboardFilter) (*DashboardStats, error)
+
+	// GetFilteredTopUsernames returns top usernames with optional filters applied.
+	GetFilteredTopUsernames(ctx context.Context, limit int, f DashboardFilter) ([]TopEntry, error)
+
+	// GetFilteredTopPasswords returns top passwords with optional filters applied.
+	GetFilteredTopPasswords(ctx context.Context, limit int, f DashboardFilter) ([]TopEntry, error)
+
+	// GetFilteredTopIPs returns top IPs with optional filters applied.
+	GetFilteredTopIPs(ctx context.Context, limit int, f DashboardFilter) ([]TopEntry, error)
+
+	// GetFilteredTopCountries returns top countries with optional filters applied.
+	GetFilteredTopCountries(ctx context.Context, limit int, f DashboardFilter) ([]TopEntry, error)
+
 	// Close releases any resources held by the store.
 	Close() error
 }