feat(skilltree): add achievement system with 26 achievements + monetization report

Full-stack achievement system for SkillTree with backend (NestJS) and frontend (SvelteKit):
- 26 achievements across 7 categories (XP, Skills, Levels, Activities, Streak, Branches, Special)
- 5 rarity tiers (Common → Legendary) with distinct styling
- Auto-unlock after XP gain, skill creation, and activity logging
- Celebration animation on unlock with sparkle effects
- Achievements page with category filters and progress tracking
- IndexedDB offline support with local condition evaluation
- Backend seeds achievements on startup, checks conditions after mutations
- Stats overview extended with achievement counter
- i18n translations (DE + EN)

Also adds docs/MONETIZATION_REPORT.md with ranked analysis of all apps.

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

scripts/mac-mini/tune-tcp.sh

@@ -0,0 +1,95 @@
+#!/bin/bash
+# tune-tcp.sh — Reduce TCP TIME_WAIT accumulation on macOS
+#
+# Problem: With 72+ Docker containers each running health checks,
+# TIME_WAIT sockets accumulate and can exhaust ephemeral ports.
+#
+# macOS default MSL (Maximum Segment Lifetime) is 15000ms (15s),
+# meaning TIME_WAIT lasts 30s (2x MSL). This script reduces MSL
+# to 5000ms (5s), so TIME_WAIT drops to 10s.
+#
+# Usage:
+#   sudo ./tune-tcp.sh          # Apply settings
+#   ./tune-tcp.sh --status      # Check current values (no sudo needed)
+#
+# To run at boot, add to a launchd plist or call from startup.sh
+
+set -euo pipefail
+
+RED='\033[0;31m'
+GREEN='\033[0;32m'
+YELLOW='\033[1;33m'
+NC='\033[0m'
+
+show_status() {
+    echo "=== TCP Tuning Status ==="
+    echo ""
+
+    # Current MSL value
+    CURRENT_MSL=$(sysctl -n net.inet.tcp.msl 2>/dev/null || echo "unknown")
+    echo -e "net.inet.tcp.msl:        ${YELLOW}${CURRENT_MSL}${NC} ms (TIME_WAIT = 2x MSL = $((CURRENT_MSL * 2 / 1000))s)"
+
+    # TIME_WAIT socket count
+    TW_COUNT=$(netstat -n -p tcp 2>/dev/null | grep -c TIME_WAIT || echo "0")
+    if [ "$TW_COUNT" -gt 500 ]; then
+        echo -e "TIME_WAIT sockets:       ${RED}${TW_COUNT}${NC} (high!)"
+    elif [ "$TW_COUNT" -gt 100 ]; then
+        echo -e "TIME_WAIT sockets:       ${YELLOW}${TW_COUNT}${NC} (moderate)"
+    else
+        echo -e "TIME_WAIT sockets:       ${GREEN}${TW_COUNT}${NC} (healthy)"
+    fi
+
+    # Ephemeral port range
+    FIRST=$(sysctl -n net.inet.ip.portrange.first 2>/dev/null || echo "unknown")
+    LAST=$(sysctl -n net.inet.ip.portrange.last 2>/dev/null || echo "unknown")
+    if [ "$FIRST" != "unknown" ] && [ "$LAST" != "unknown" ]; then
+        AVAILABLE=$((LAST - FIRST))
+        echo -e "Ephemeral port range:    ${FIRST}-${LAST} (${AVAILABLE} ports)"
+        if [ "$TW_COUNT" != "0" ] && [ "$AVAILABLE" -gt 0 ]; then
+            USAGE_PCT=$((TW_COUNT * 100 / AVAILABLE))
+            echo -e "Port usage by TIME_WAIT: ${USAGE_PCT}%"
+        fi
+    fi
+
+    echo ""
+}
+
+apply_settings() {
+    if [ "$(id -u)" -ne 0 ]; then
+        echo -e "${RED}Error: Must run as root (sudo) to change sysctl values${NC}"
+        echo "Usage: sudo $0"
+        exit 1
+    fi
+
+    echo "=== Applying TCP Tuning ==="
+    echo ""
+
+    # Show before
+    BEFORE_MSL=$(sysctl -n net.inet.tcp.msl 2>/dev/null)
+    echo "Before: net.inet.tcp.msl = ${BEFORE_MSL}ms (TIME_WAIT = $((BEFORE_MSL * 2 / 1000))s)"
+
+    # Set MSL to 5000ms (TIME_WAIT will be 10s instead of 30s)
+    sysctl -w net.inet.tcp.msl=5000
+
+    # Show after
+    AFTER_MSL=$(sysctl -n net.inet.tcp.msl 2>/dev/null)
+    echo -e "After:  net.inet.tcp.msl = ${GREEN}${AFTER_MSL}${NC}ms (TIME_WAIT = $((AFTER_MSL * 2 / 1000))s)"
+
+    echo ""
+    echo -e "${GREEN}TCP tuning applied successfully.${NC}"
+    echo "Note: This setting does not persist across reboots."
+    echo "Add this script to startup.sh or a launchd plist for persistence."
+    echo ""
+
+    show_status
+}
+
+# Main
+case "${1:-apply}" in
+    --status|-s|status)
+        show_status
+        ;;
+    *)
+        apply_settings
+        ;;
+esac