feat: Space Booking System - MVP complet

Sistem web pentru rezervarea de birouri și săli de ședință
cu flux de aprobare administrativă.

Stack: FastAPI + Vue.js 3 + SQLite + TypeScript

Features implementate:
- Autentificare JWT + Self-registration cu email verification
- CRUD Spații, Utilizatori, Settings (Admin)
- Calendar interactiv (FullCalendar) cu drag-and-drop
- Creare rezervări cu validare (durată, program, overlap, max/zi)
- Rezervări recurente (săptămânal)
- Admin: aprobare/respingere/anulare cereri
- Admin: creare directă rezervări (bypass approval)
- Admin: editare orice rezervare
- User: editare/anulare rezervări proprii
- Notificări in-app (bell icon + dropdown)
- Notificări email (async SMTP cu BackgroundTasks)
- Jurnal acțiuni administrative (audit log)
- Rapoarte avansate (utilizare, top users, approval rate)
- Șabloane rezervări (booking templates)
- Atașamente fișiere (upload/download)
- Conflict warnings (verificare disponibilitate real-time)
- Integrare Google Calendar (OAuth2)
- Suport timezone (UTC storage + user preference)
- 225+ teste backend

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

backend/app/utils/__init__.py

@@ -0,0 +1 @@
+"""Utilities module."""

backend/app/utils/timezone.py

@@ -0,0 +1,79 @@
+"""Timezone utilities for converting between UTC and user timezones."""
+from datetime import datetime
+from typing import Optional
+import pytz
+from dateutil import parser
+
+
+def convert_to_utc(dt: datetime, from_timezone: str = "UTC") -> datetime:
+    """Convert datetime from user timezone to UTC.
+
+    Args:
+        dt: Datetime to convert (naive or aware)
+        from_timezone: IANA timezone name (e.g., "Europe/Bucharest")
+
+    Returns:
+        Naive datetime in UTC
+    """
+    if dt.tzinfo is None:
+        # Naive datetime, assume it's in user timezone
+        tz = pytz.timezone(from_timezone)
+        dt = tz.localize(dt)
+
+    # Convert to UTC
+    return dt.astimezone(pytz.UTC).replace(tzinfo=None)
+
+
+def convert_from_utc(dt: datetime, to_timezone: str = "UTC") -> datetime:
+    """Convert datetime from UTC to user timezone.
+
+    Args:
+        dt: Datetime in UTC (naive or aware)
+        to_timezone: IANA timezone name (e.g., "Europe/Bucharest")
+
+    Returns:
+        Timezone-aware datetime in target timezone
+    """
+    if dt.tzinfo is None:
+        # Add UTC timezone if naive
+        dt = pytz.UTC.localize(dt)
+
+    # Convert to target timezone
+    tz = pytz.timezone(to_timezone)
+    return dt.astimezone(tz)
+
+
+def format_datetime_tz(dt: datetime, timezone: str = "UTC", format_str: str = "%Y-%m-%d %H:%M %Z") -> str:
+    """Format datetime with timezone abbreviation.
+
+    Args:
+        dt: Datetime in UTC (naive or aware)
+        timezone: IANA timezone name for display
+        format_str: Format string (default includes timezone abbreviation)
+
+    Returns:
+        Formatted datetime string with timezone
+    """
+    dt_tz = convert_from_utc(dt, timezone)
+    return dt_tz.strftime(format_str)
+
+
+def get_available_timezones():
+    """Get list of common timezones for user selection."""
+    common_timezones = [
+        "UTC",
+        "Europe/Bucharest",
+        "Europe/London",
+        "Europe/Paris",
+        "Europe/Berlin",
+        "Europe/Amsterdam",
+        "America/New_York",
+        "America/Los_Angeles",
+        "America/Chicago",
+        "America/Denver",
+        "Asia/Tokyo",
+        "Asia/Shanghai",
+        "Asia/Dubai",
+        "Australia/Sydney",
+    ]
+    return common_timezones