feat: implement comprehensive gamification, analytics, and leaderboard system

This commit adds a complete gamification system with analytics dashboards,
leaderboards, and enhanced badge tracking functionality.

Backend Features:
- Analytics API with overview, user stats, activity trends, top contributors,
  and street statistics endpoints
- Leaderboard API supporting global, weekly, monthly, and friends views
- Profile API for viewing and managing user profiles
- Enhanced gamification service with badge progress tracking and user stats
- Comprehensive test coverage for analytics and leaderboard endpoints
- Profile validation middleware for secure profile updates

Frontend Features:
- Analytics dashboard with multiple tabs (Overview, Activity, Personal Stats)
- Interactive charts for activity trends and street statistics
- Leaderboard component with pagination and timeframe filtering
- Badge collection display with progress tracking
- Personal stats component showing user achievements
- Contributors list for top performing users
- Profile management components (View/Edit)
- Toast notifications integrated throughout
- Comprehensive test coverage for Leaderboard component

Enhancements:
- User model enhanced with stats tracking and badge management
- Fixed express.Router() capitalization bug in users route
- Badge service improvements for better criteria matching
- Removed unused imports in Profile component

This feature enables users to track their contributions, view community
analytics, compete on leaderboards, and earn badges for achievements.

🤖 Generated with OpenCode

Co-Authored-By: AI Assistant <noreply@opencode.ai>

frontend/src/components/BadgeDisplay.js

@@ -0,0 +1,88 @@
+import React from "react";
+import PropTypes from "prop-types";
+
+/**
+ * BadgeDisplay component - displays a single badge with icon, name, and description
+ * @param {Object} badge - Badge object
+ * @param {boolean} isEarned - Whether the badge is earned
+ * @param {boolean} showTooltip - Whether to show tooltip on hover
+ */
+const BadgeDisplay = ({ badge, isEarned = false, showTooltip = true }) => {
+  const getRarityColor = (rarity) => {
+    switch (rarity) {
+      case "common":
+        return "#6c757d";
+      case "rare":
+        return "#0d6efd";
+      case "epic":
+        return "#6f42c1";
+      case "legendary":
+        return "#ffc107";
+      default:
+        return "#6c757d";
+    }
+  };
+
+  const badgeStyle = {
+    filter: isEarned ? "none" : "grayscale(100%) opacity(0.5)",
+    borderColor: getRarityColor(badge.rarity),
+    borderWidth: "3px",
+    transition: "all 0.3s ease",
+  };
+
+  const iconStyle = {
+    fontSize: "3rem",
+    marginBottom: "0.5rem",
+  };
+
+  return (
+    <div
+      className="card badge-card text-center p-3"
+      style={badgeStyle}
+      title={
+        showTooltip
+          ? `${badge.name} - ${badge.description}\n${
+              badge.criteria?.type
+                ? `Unlock: ${badge.criteria.threshold} ${badge.criteria.type.replace(
+                    "_",
+                    " "
+                  )}`
+                : ""
+            }`
+          : ""
+      }
+    >
+      <div style={iconStyle}>{badge.icon || "🏆"}</div>
+      <h6 className="mb-1">{badge.name}</h6>
+      <p className="small text-muted mb-1">{badge.description}</p>
+      <span
+        className={`badge badge-${badge.rarity === "legendary" ? "warning" : badge.rarity === "epic" ? "purple" : badge.rarity === "rare" ? "primary" : "secondary"}`}
+      >
+        {badge.rarity}
+      </span>
+      {isEarned && (
+        <div className="mt-2">
+          <span className="badge badge-success">✓ Earned</span>
+        </div>
+      )}
+    </div>
+  );
+};
+
+BadgeDisplay.propTypes = {
+  badge: PropTypes.shape({
+    _id: PropTypes.string.isRequired,
+    name: PropTypes.string.isRequired,
+    description: PropTypes.string.isRequired,
+    icon: PropTypes.string,
+    rarity: PropTypes.oneOf(["common", "rare", "epic", "legendary"]).isRequired,
+    criteria: PropTypes.shape({
+      type: PropTypes.string,
+      threshold: PropTypes.number,
+    }),
+  }).isRequired,
+  isEarned: PropTypes.bool,
+  showTooltip: PropTypes.bool,
+};
+
+export default BadgeDisplay;