Add new skills for backend patterns, coding standards, continuous learning, and NestJS best practices

- Introduced backend patterns skill with guidelines on API design, database optimization, and server-side best practices.
- Added coding standards skill outlining universal coding principles for TypeScript, NestJS, and Node.js development.
- Implemented continuous learning skill to automatically extract reusable patterns from Cursor sessions.
- Created NestJS best practices skill detailing architecture patterns, dependency injection, error handling, and security measures.
- Included various rules and templates for NestJS best practices to ensure production-ready applications.

.agents/skills/continuous-learning/evaluate-session.sh

@@ -0,0 +1,53 @@
+#!/bin/bash
+# Continuous Learning - Session Evaluator
+# Runs on sessionEnd to extract reusable patterns from Cursor sessions
+#
+# Configured in .cursor/hooks.json:
+#   sessionEnd -> node .cursor/scripts/hooks/evaluate-session.js
+# This shell version is a fallback.
+#
+# Extracted skills saved to: .agents/skills/learned/
+
+set -e
+
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+ROOT="$(git rev-parse --show-toplevel 2>/dev/null || pwd)"
+CONFIG_FILE="$SCRIPT_DIR/config.json"
+LEARNED_SKILLS_PATH="${ROOT}/.agents/skills/learned"
+MIN_SESSION_LENGTH=10
+
+# Load config if exists
+if [ -f "$CONFIG_FILE" ]; then
+  MIN_SESSION_LENGTH=$(jq -r '.min_session_length // 10' "$CONFIG_FILE")
+  configured_path=$(jq -r '.learned_skills_path // empty' "$CONFIG_FILE")
+  if [ -n "$configured_path" ]; then
+    LEARNED_SKILLS_PATH=$(echo "$configured_path" | sed "s|~|$HOME|")
+    case "$LEARNED_SKILLS_PATH" in
+      /*) ;;
+      *) LEARNED_SKILLS_PATH="${ROOT}/${LEARNED_SKILLS_PATH}" ;;
+    esac
+  fi
+fi
+
+# Ensure learned skills directory exists
+mkdir -p "$LEARNED_SKILLS_PATH"
+
+# Get transcript path from environment (set by Claude Code)
+transcript_path="${CLAUDE_TRANSCRIPT_PATH:-}"
+
+if [ -z "$transcript_path" ] || [ ! -f "$transcript_path" ]; then
+  exit 0
+fi
+
+# Count messages in session
+message_count=$(grep -c '"type":"user"' "$transcript_path" 2>/dev/null || echo "0")
+
+# Skip short sessions
+if [ "$message_count" -lt "$MIN_SESSION_LENGTH" ]; then
+  echo "[ContinuousLearning] Session too short ($message_count messages), skipping" >&2
+  exit 0
+fi
+
+# Signal to Claude that session should be evaluated for extractable patterns
+echo "[ContinuousLearning] Session has $message_count messages - evaluate for extractable patterns" >&2
+echo "[ContinuousLearning] Save learned skills to: $LEARNED_SKILLS_PATH" >&2