ci: add worker validation and Docker build checks

Add automated validation to prevent worker-related issues:

**Worker Validation Script:**
- New script: .github/scripts/validate-workers.sh
- Validates all workers in docker-compose.yml exist
- Checks required files: Dockerfile, requirements.txt, worker.py
- Verifies files are tracked by git (not gitignored)
- Detects gitignore issues that could hide workers

**CI Workflow Updates:**
- Added validate-workers job (runs on every PR)
- Added build-workers job (runs if workers/ modified)
- Uses Docker Buildx for caching
- Validates Docker images build successfully
- Updated test-summary to check validation results

**PR Template:**
- New pull request template with comprehensive checklist
- Specific section for worker-related changes
- Reminds contributors to validate worker files
- Includes documentation and changelog reminders

These checks would have caught the secrets worker gitignore issue.

Implements Phase 1 improvements from CI/CD quality assessment.

.github/scripts/validate-workers.sh

@@ -0,0 +1,95 @@
+#!/bin/bash
+# Worker Validation Script
+# Ensures all workers defined in docker-compose.yml exist in the repository
+# and are properly tracked by git.
+
+set -e
+
+echo "🔍 Validating worker completeness..."
+
+# Colors for output
+RED='\033[0;31m'
+GREEN='\033[0;32m'
+YELLOW='\033[1;33m'
+NC='\033[0m' # No Color
+
+ERRORS=0
+WARNINGS=0
+
+# Extract worker service names from docker-compose.yml
+echo ""
+echo "📋 Checking workers defined in docker-compose.yml..."
+WORKERS=$(grep -E "^\s+worker-" docker-compose.yml | grep -v "#" | cut -d: -f1 | tr -d ' ' | sort -u)
+
+if [ -z "$WORKERS" ]; then
+    echo -e "${RED}❌ No workers found in docker-compose.yml${NC}"
+    exit 1
+fi
+
+echo "Found workers:"
+for worker in $WORKERS; do
+    echo "  - $worker"
+done
+
+# Check each worker
+echo ""
+echo "🔎 Validating worker files..."
+for worker in $WORKERS; do
+    WORKER_DIR="workers/${worker#worker-}"
+
+    echo ""
+    echo "Checking $worker ($WORKER_DIR)..."
+
+    # Check if directory exists
+    if [ ! -d "$WORKER_DIR" ]; then
+        echo -e "${RED}  ❌ Directory not found: $WORKER_DIR${NC}"
+        ERRORS=$((ERRORS + 1))
+        continue
+    fi
+
+    # Check required files
+    REQUIRED_FILES=("Dockerfile" "requirements.txt" "worker.py")
+    for file in "${REQUIRED_FILES[@]}"; do
+        FILE_PATH="$WORKER_DIR/$file"
+
+        if [ ! -f "$FILE_PATH" ]; then
+            echo -e "${RED}  ❌ Missing file: $FILE_PATH${NC}"
+            ERRORS=$((ERRORS + 1))
+        else
+            # Check if file is tracked by git
+            if ! git ls-files --error-unmatch "$FILE_PATH" &> /dev/null; then
+                echo -e "${RED}  ❌ File not tracked by git: $FILE_PATH${NC}"
+                echo -e "${YELLOW}     Check .gitignore patterns!${NC}"
+                ERRORS=$((ERRORS + 1))
+            else
+                echo -e "${GREEN}  ✓ $file (tracked)${NC}"
+            fi
+        fi
+    done
+done
+
+# Check for any ignored worker files
+echo ""
+echo "🚫 Checking for gitignored worker files..."
+IGNORED_FILES=$(git check-ignore workers/*/* 2>/dev/null || true)
+if [ -n "$IGNORED_FILES" ]; then
+    echo -e "${YELLOW}⚠️  Warning: Some worker files are being ignored:${NC}"
+    echo "$IGNORED_FILES" | while read -r file; do
+        echo -e "${YELLOW}  - $file${NC}"
+    done
+    WARNINGS=$((WARNINGS + 1))
+fi
+
+# Summary
+echo ""
+echo "━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━"
+if [ $ERRORS -eq 0 ] && [ $WARNINGS -eq 0 ]; then
+    echo -e "${GREEN}✅ All workers validated successfully!${NC}"
+    exit 0
+elif [ $ERRORS -eq 0 ]; then
+    echo -e "${YELLOW}⚠️  Validation passed with $WARNINGS warning(s)${NC}"
+    exit 0
+else
+    echo -e "${RED}❌ Validation failed with $ERRORS error(s) and $WARNINGS warning(s)${NC}"
+    exit 1
+fi