Fix: Make CI .env manipulation robust against missing trailing newlines (#15189)

## Problem

CI workflow started timing out on October 14, 2025 after commit
`d750df7fff` removed the trailing newline from `.env.example`.

## Root Cause

When `.env.example` lacks a trailing newline:
```bash
# Last line without newline
# CLICKHOUSE_URL=...twenty
```

And CI runs:
```bash
echo "NODE_PORT=3002" >> .env
```

Result:
```bash
# CLICKHOUSE_URL=...twentyNODE_PORT=3002  ← Commented out!
```

Server starts on default port 3000 instead of 3002, health check fails.

## Fix

1. **Restore trailing newline** to `.env.example`
2. **Make all CI `.env` operations robust** by adding `echo "" >> .env`
before appending
3. **Simplified `set_env_var`** function to always add newline first

Now works regardless of whether template files have trailing newlines.

## Files Changed

- 6 CI workflow files
- 1 .env.example file

.github/workflows/ci-breaking-changes.yaml

@@ -124,13 +124,14 @@ jobs:
       - name: Setup current branch database
         run: |
           npx nx reset:env twenty-server
-          # Function to set or update environment variable
           set_env_var() {
             local var_name="$1"
             local var_value="$2"
             local env_file="packages/twenty-server/.env"
             
-            if grep -q "^${var_name}=" "$env_file"; then
+            echo "" >> "$env_file"
+            
+            if grep -q "^${var_name}=" "$env_file" 2>/dev/null; then
               sed -i "s|^${var_name}=.*|${var_name}=${var_value}|" "$env_file"
             else
               echo "${var_name}=${var_value}" >> "$env_file"
@@ -276,13 +277,14 @@ jobs:
       - name: Setup main branch database
         run: |
           npx nx reset:env twenty-server
-          # Function to set or update environment variable
           set_env_var() {
             local var_name="$1"
             local var_value="$2"
             local env_file="packages/twenty-server/.env"
             
-            if grep -q "^${var_name}=" "$env_file"; then
+            echo "" >> "$env_file"
+            
+            if grep -q "^${var_name}=" "$env_file" 2>/dev/null; then
               sed -i "s|^${var_name}=.*|${var_name}=${var_value}|" "$env_file"
             else
               echo "${var_name}=${var_value}" >> "$env_file"