feat: frontend LOG_LEVEL support via logger utility (#209)

- Inject LOG_LEVEL at build time via Vite define (__LOG_LEVEL__, default: warn)
- Create frontend logger utility (frontend/src/utils/logger.ts) mirroring backend API
- Replace all console.error calls with log.error in MedicationsPage, AppContext, Auth
- Supports levels: silent > error > warn > info > debug

Closes #205

frontend/src/utils/logger.ts

@@ -0,0 +1,39 @@
+/**
+ * Frontend logger that respects LOG_LEVEL (injected at build time via Vite define).
+ * Mirrors the backend logger API so usage is consistent across the stack.
+ *
+ * Levels (high → low): silent > error > warn > info > debug
+ * Default: "warn" — only warn and error messages are shown.
+ */
+
+declare const __LOG_LEVEL__: string;
+
+const LOG_LEVELS: Record<string, number> = {
+	silent: 50,
+	error: 40,
+	warn: 30,
+	info: 20,
+	debug: 10,
+};
+
+const configuredLevel = typeof __LOG_LEVEL__ !== "undefined" ? __LOG_LEVEL__.toLowerCase() : "warn";
+const threshold = LOG_LEVELS[configuredLevel] ?? LOG_LEVELS.warn;
+
+function shouldLog(level: string): boolean {
+	return (LOG_LEVELS[level] ?? 0) >= threshold;
+}
+
+export const log = {
+	debug(...args: unknown[]): void {
+		if (shouldLog("debug")) console.debug(...args);
+	},
+	info(...args: unknown[]): void {
+		if (shouldLog("info")) console.info(...args);
+	},
+	warn(...args: unknown[]): void {
+		if (shouldLog("warn")) console.warn(...args);
+	},
+	error(...args: unknown[]): void {
+		if (shouldLog("error")) console.error(...args);
+	},
+};