chore: beta release v0.5.0-beta

- Bump version to 0.5.0-beta
- Add Apache-2.0 LICENSE (official text) + NOTICE
- Add Docker support: multi-stage Dockerfile + docker-compose
  * non-root user, tini PID 1, gunicorn + uvicorn workers
  * healthcheck, OCI labels, persistent /data volume
- Add GitHub Actions CI (lint/import-check + Docker smoke-test)
- Backend polish:
  * modern lifespan handler (replaces deprecated on_event)
  * explicit sort validation (400 instead of 500)
  * title min_length=1 schema validation
  * configurable data dir + http timeout via env
  * avg_rating helper extracted (DRY)
- Frontend polish:
  * beta badge in title, footer with live version
  * loading spinner on initial fetch
  * updated README, badges, config table, roadmap

app/schemas.py

@@ -1,4 +1,5 @@
 """Pydantic-Schemas für API-Ein- und -Ausgabe."""
+# SPDX-License-Identifier: Apache-2.0
 from __future__ import annotations
 
 from datetime import date, datetime
@@ -7,15 +8,17 @@ from typing import List, Literal, Optional
 from pydantic import BaseModel, ConfigDict, Field
 
 
-# ---------- Eingaben ---------------------------------------------------------
+# ---------- Typen ------------------------------------------------------------
 
 MediaKind = Literal["book", "series"]
 MediaStatus = Literal["plan", "reading", "done", "hold", "dropped"]
 
 
+# ---------- Eingaben ---------------------------------------------------------
+
 class MediaBase(BaseModel):
     kind: MediaKind
-    title: str = Field(..., max_length=200)
+    title: str = Field(..., max_length=200, min_length=1)
     original_title: Optional[str] = Field(None, max_length=200)
     description: Optional[str] = None
     cover_url: Optional[str] = Field(None, max_length=600)
@@ -53,7 +56,7 @@ class MediaCreate(MediaBase):
 
 class MediaUpdate(BaseModel):
     """Alle Felder optional – PATCH-Semantik."""
-    title: Optional[str] = Field(None, max_length=200)
+    title: Optional[str] = Field(None, max_length=200, min_length=1)
     original_title: Optional[str] = None
     description: Optional[str] = None
     cover_url: Optional[str] = None