🐛 fix: emit all config-loading logs in correct JSON format from the start (#16)

## Summary

Closes #15

When `logging.json: true` (or `DLC_LOGGING_JSON=true`), the logger was unconditionally initialised to console/text format at the top of `LoadConfig()`, so early log lines — most visibly **"Config file loaded"** — were always written as human-readable text regardless of configuration.

## Root cause

Classic chicken-and-egg: the format flag lives inside the config that is being loaded. The format-switch block only ran *after* `v.Unmarshal()`, too late for the config-file log.

## Changes

### `pkg/config/config.go`
- Add `peekJSONLogging()`: resolves the JSON flag **before** any log is emitted by (1) checking `DLC_LOGGING_JSON` directly via `os.Getenv`, then (2) doing a minimal throwaway Viper pre-read of the config file for the `logging.json` key. This mirrors Viper's own priority order without parsing the full config twice.
- Apply the resolved format immediately and emit **"Logging configured"** as the very first log line.
- Remove the now-redundant format-switch block that ran after `Unmarshal()`.

### `scripts/start-server.sh`, `test-graceful-shutdown.sh`, `test-opentelemetry.sh`
- Replace hardcoded `PROJECT_DIR` path with a dynamic `SCRIPTS_DIR=$(dirname $(realpath ${BASH_SOURCE[0]}))` derivation so scripts work from any worktree or clone location.

## Test plan
- [x] `go test ./pkg/...` — all pass
- [x] `scripts/test-graceful-shutdown.sh` — all JSON valid, all startup logs present
- [x] Manual smoke test: first line is `{"level":"info",...,"message":"Logging configured"}`, every line is valid JSON

Reviewed-on: #16
Co-authored-by: Gabriel Radureau <arcodange@gmail.com>
Co-committed-by: Gabriel Radureau <arcodange@gmail.com>

scripts/start-server.sh

@@ -4,7 +4,8 @@
 # This script starts the server in the background and provides control functions
 
 # Configuration
-PROJECT_DIR="/Users/gabrielradureau/Work/Vibe/dance-lessons-coach"
+SCRIPTS_DIR=$(dirname "$(realpath "${BASH_SOURCE[0]}")")
+PROJECT_DIR=$(dirname "$SCRIPTS_DIR")
 SERVER_CMD="go run ./cmd/server"
 LOG_FILE="server.log"
 PID_FILE="server.pid"

scripts/test-graceful-shutdown.sh

@@ -7,7 +7,8 @@
 set -e
 
 # Configuration
-PROJECT_DIR="/Users/gabrielradureau/Work/Vibe/dance-lessons-coach"
+SCRIPTS_DIR=$(dirname "$(realpath "${BASH_SOURCE[0]}")")
+PROJECT_DIR=$(dirname "$SCRIPTS_DIR")
 SERVER_CMD="./scripts/start-server.sh"
 LOG_FILE="server.log"
 PID_FILE="server.pid"
@@ -59,11 +60,40 @@ echo "Response: $GREET_NAME_RESPONSE"
 echo ""
 echo "Stopping server gracefully..."
 
-# Test readiness during shutdown (in background)
-(curl -s http://localhost:8080/api/ready > /dev/null 2>&1 &)
+# Send SIGTERM once and probe /api/ready during the 1-second propagation window
+# the server holds open (pkg/server/server.go: time.Sleep(1s) after readiness
+# cancel). Previously the curl fired *before* the signal — it always saw "ready".
+# We also avoid calling "$SERVER_CMD stop" afterwards because that would send a
+# second SIGTERM: after signal.NotifyContext is done, the default handler kicks in
+# and the process terminates with a non-JSON "signal: terminated" on stderr.
+SERVER_PID=$(cat "$PID_FILE" 2>/dev/null || echo "")
+if [[ -z "$SERVER_PID" ]]; then
+    echo -e "\033[0;31m❌ FAIL: PID file not found\033[0m"
+    exit 1
+fi
 
-$SERVER_CMD stop
-sleep 3
+kill -TERM "$SERVER_PID"
+# Brief yield so the signal handler runs and CancelableContext.Cancel() fires
+sleep 0.2
+READY_DURING_SHUTDOWN=$(curl -s -w "\n[HTTP %{http_code}]" http://localhost:8080/api/ready 2>&1 || echo "[connection refused]")
+echo "Readiness during shutdown: $READY_DURING_SHUTDOWN"
+
+# Wait for the process to exit cleanly (up to 30s) without sending another signal
+echo "Waiting for server to exit..."
+for i in {1..30}; do
+    if ! ps -p "$SERVER_PID" > /dev/null 2>&1; then
+        echo "Server stopped successfully"
+        rm -f "$PID_FILE"
+        break
+    fi
+    sleep 1
+done
+if ps -p "$SERVER_PID" > /dev/null 2>&1; then
+    echo -e "\033[0;31m❌ FAIL: Server did not stop within 30s\033[0m"
+    kill -9 "$SERVER_PID" 2>/dev/null || true
+    exit 1
+fi
+sleep 0.5
 
 echo ""
 echo "Analyzing server logs..."
@@ -201,6 +231,12 @@ fi
 echo ""
 echo -e "\033[0;32m🎉 GRACEFUL SHUTDOWN TEST PASSED!\033[0m"
 echo "All required logs are present and in correct order."
+
+echo ""
+echo "📋 Full server log:"
+echo "==============================="
+cat "$LOG_FILE" | jq -r '"[\(.level | ascii_upcase)] \(.time | tostring) — \(.message)"'
+echo "==============================="
 echo ""
 
 # Clean up

scripts/test-opentelemetry.sh

@@ -9,7 +9,8 @@ echo -e "\033[1;34m=== dance-lessons-coach OpenTelemetry Test ===\033[0m"
 echo ""
 
 # Configuration
-PROJECT_DIR="/Users/gabrielradureau/Work/Vibe/dance-lessons-coach"
+SCRIPTS_DIR=$(dirname "$(realpath "${BASH_SOURCE[0]}")")
+PROJECT_DIR=$(dirname "$SCRIPTS_DIR")
 SERVER_CMD="./scripts/start-server.sh"
 LOG_FILE="server.log"
 PID_FILE="server.pid"