feat: add open/closed state filter to PR list view

Mirror the existing issues state filter pattern: read state query param
(default "open"), pass it to ListAllPullRequests instead of hardcoded
"open", and add a state select widget to the pulls filter bar with
proper hx-include for HTMX partial reloads and infinite scroll.

Closes leeworks-agents/gitea-mobile#72

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

internal/handlers/handlers.go

@@ -320,23 +320,29 @@ func (h *Handler) ListPulls(w http.ResponseWriter, r *http.Request) {
 	orgNames := h.getUserOrgs(r)
 
 	type pullsData struct {
-		Pulls       []giteaclient.PullRequest
-		Orgs        []string
-		SelectedOrg string
-		HasMore     bool
-		NextPage    int
-		Error       string
+		Pulls         []giteaclient.PullRequest
+		Orgs          []string
+		SelectedOrg   string
+		SelectedState string
+		HasMore       bool
+		NextPage      int
+		Error         string
 	}
 
 	selectedOrg := r.URL.Query().Get("org")
+	selectedState := r.URL.Query().Get("state")
+	if selectedState == "" {
+		selectedState = "open"
+	}
 	page, _ := strconv.Atoi(r.URL.Query().Get("page"))
 	if page < 1 {
 		page = 1
 	}
 
 	data := pullsData{
-		Orgs:        orgNames,
-		SelectedOrg: selectedOrg,
+		Orgs:          orgNames,
+		SelectedOrg:   selectedOrg,
+		SelectedState: selectedState,
 	}
 
 	if len(orgNames) == 0 {
@@ -347,7 +353,7 @@ func (h *Handler) ListPulls(w http.ResponseWriter, r *http.Request) {
 			queryOrgs = []string{selectedOrg}
 		}
 
-		result, err := h.Client.ListAllPullRequests(r.Context(), token, queryOrgs, "open", page)
+		result, err := h.Client.ListAllPullRequests(r.Context(), token, queryOrgs, selectedState, page)
 		if err != nil {
 			slog.Error("failed to list pull requests", "error", err)
 			data.Error = "Error loading pull requests."