Add service information feature with version checks

This commit introduces a new "Service Information" section displaying runtime details, installed version, and update status for the NexaPG application. It includes backend API endpoints, database schema changes, and a corresponding frontend page that allows users to check for updates against the official repository. The `.env` example now includes an `APP_VERSION` variable, and related documentation has been updated.

backend/app/api/routes/service_info.py

@@ -0,0 +1,105 @@
+import os
+import platform
+from datetime import datetime, timezone
+
+from fastapi import APIRouter, Depends
+from sqlalchemy import select
+from sqlalchemy.ext.asyncio import AsyncSession
+
+from app.core.config import get_settings
+from app.core.db import get_db
+from app.core.deps import get_current_user
+from app.models.models import ServiceInfoSettings, User
+from app.schemas.service_info import ServiceInfoCheckResult, ServiceInfoOut
+from app.services.audit import write_audit_log
+from app.services.service_info import (
+    UPSTREAM_REPO_WEB,
+    fetch_latest_from_upstream,
+    is_update_available,
+    utcnow,
+)
+
+router = APIRouter()
+settings = get_settings()
+service_started_at = datetime.now(timezone.utc)
+
+
+async def _get_or_create_service_settings(db: AsyncSession) -> ServiceInfoSettings:
+    row = await db.scalar(select(ServiceInfoSettings).limit(1))
+    if row:
+        return row
+    row = ServiceInfoSettings(current_version=settings.app_version)
+    db.add(row)
+    await db.commit()
+    await db.refresh(row)
+    return row
+
+
+def _to_out(row: ServiceInfoSettings) -> ServiceInfoOut:
+    uptime_seconds = int((utcnow() - service_started_at).total_seconds())
+    return ServiceInfoOut(
+        app_name=settings.app_name,
+        environment=settings.environment,
+        api_prefix=settings.api_v1_prefix,
+        app_version=settings.app_version,
+        hostname=platform.node() or os.getenv("HOSTNAME", "unknown"),
+        python_version=platform.python_version(),
+        platform=platform.platform(),
+        service_started_at=service_started_at,
+        uptime_seconds=max(uptime_seconds, 0),
+        update_source=UPSTREAM_REPO_WEB,
+        latest_version=row.latest_version,
+        latest_ref=(row.release_check_url or None),
+        update_available=row.update_available,
+        last_checked_at=row.last_checked_at,
+        last_check_error=row.last_check_error,
+    )
+
+
+@router.get("/info", response_model=ServiceInfoOut)
+async def get_service_info(
+    user: User = Depends(get_current_user),
+    db: AsyncSession = Depends(get_db),
+) -> ServiceInfoOut:
+    _ = user
+    row = await _get_or_create_service_settings(db)
+    return _to_out(row)
+
+
+@router.post("/info/check", response_model=ServiceInfoCheckResult)
+async def check_service_version(
+    user: User = Depends(get_current_user),
+    db: AsyncSession = Depends(get_db),
+) -> ServiceInfoCheckResult:
+    row = await _get_or_create_service_settings(db)
+    check_time = utcnow()
+    latest, latest_ref, error = await fetch_latest_from_upstream()
+
+    row.last_checked_at = check_time
+    row.last_check_error = error
+    if latest:
+        row.latest_version = latest
+        row.release_check_url = latest_ref
+        row.update_available = is_update_available(settings.app_version, latest)
+    else:
+        row.update_available = False
+    await db.commit()
+    await db.refresh(row)
+    await write_audit_log(
+        db,
+        "service.info.check",
+        user.id,
+        {
+            "latest_version": row.latest_version,
+            "latest_ref": row.release_check_url,
+            "update_available": row.update_available,
+            "last_check_error": row.last_check_error,
+        },
+    )
+    return ServiceInfoCheckResult(
+        latest_version=row.latest_version,
+        latest_ref=(row.release_check_url or None),
+        update_available=row.update_available,
+        last_checked_at=row.last_checked_at or check_time,
+        last_check_error=row.last_check_error,
+    )