feat(phase7): per-channel notification settings and read receipts

Phase 7.1 — Per-channel notification settings
- New notification_settings table (user_id, channel_id, level)
- GET/PUT/DELETE handlers under /channels/{channelID}/notifications
- Push dispatch and @mention loops filtered by notification level
- Frontend: bell icon per channel cycling all/mentions/none

Phase 7.4 — Read receipts
- New read_states table (user_id, channel_id, last_read_message_id)
- PUT /channels/{channelID}/read and GET /users/me/read-states
- Auto-mark-read when messages load in ChatArea
- Unread dot for channels never opened

Also: favicon/icon refresh in index.html

internal/readstate/handlers.go

@@ -0,0 +1,94 @@
+package readstate
+
+import (
+	"database/sql"
+	"encoding/json"
+	"log/slog"
+	"net/http"
+
+	"git.dustin.coffee/hobokenchicken/dumpsterChat/internal/middleware"
+	"github.com/go-chi/chi/v5"
+)
+
+type Handler struct {
+	db     *sql.DB
+	logger *slog.Logger
+}
+
+func NewHandler(db *sql.DB, logger *slog.Logger) *Handler {
+	return &Handler{db: db, logger: logger}
+}
+
+func (h *Handler) RegisterRoutes(r chi.Router) {
+	r.Put("/{channelID}/read", h.MarkRead)
+	r.Get("/users/me/read-states", h.GetAll)
+}
+
+type markReadRequest struct {
+	LastReadMessageID string `json:"last_read_message_id"`
+}
+
+func (h *Handler) MarkRead(w http.ResponseWriter, r *http.Request) {
+	userID, _ := middleware.UserIDFromContext(r.Context())
+	channelID := chi.URLParam(r, "channelID")
+
+	var req markReadRequest
+	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
+		http.Error(w, `{"error":"invalid JSON"}`, http.StatusBadRequest)
+		return
+	}
+	if req.LastReadMessageID == "" {
+		http.Error(w, `{"error":"last_read_message_id is required"}`, http.StatusBadRequest)
+		return
+	}
+
+	_, err := h.db.Exec(`
+		INSERT INTO read_states (user_id, channel_id, last_read_message_id, updated_at)
+		VALUES ($1, $2, $3, NOW())
+		ON CONFLICT (user_id, channel_id) DO UPDATE SET
+			last_read_message_id = $3,
+			updated_at = NOW()
+	`, userID, channelID, req.LastReadMessageID)
+	if err != nil {
+		h.logger.Error("failed to mark read", "error", err)
+		http.Error(w, `{"error":"internal error"}`, http.StatusInternalServerError)
+		return
+	}
+
+	w.Header().Set("Content-Type", "application/json")
+	json.NewEncoder(w).Encode(map[string]string{"status": "ok"})
+}
+
+// ChannelReadState is returned per channel
+type ChannelReadState struct {
+	ChannelID          string `json:"channel_id"`
+	LastReadMessageID  string `json:"last_read_message_id"`
+}
+
+func (h *Handler) GetAll(w http.ResponseWriter, r *http.Request) {
+	userID, _ := middleware.UserIDFromContext(r.Context())
+
+	rows, err := h.db.Query(`
+		SELECT rs.channel_id, rs.last_read_message_id
+		FROM read_states rs
+		WHERE rs.user_id = $1
+	`, userID)
+	if err != nil {
+		h.logger.Error("failed to query read states", "error", err)
+		http.Error(w, `{"error":"internal error"}`, http.StatusInternalServerError)
+		return
+	}
+	defer rows.Close()
+
+	states := make(map[string]string)
+	for rows.Next() {
+		var channelID, lastReadMessageID string
+		if err := rows.Scan(&channelID, &lastReadMessageID); err != nil {
+			continue
+		}
+		states[channelID] = lastReadMessageID
+	}
+
+	w.Header().Set("Content-Type", "application/json")
+	json.NewEncoder(w).Encode(states)
+}