Fix bugs across app + server, optimize UI/UX, add Gitea CI

Bug fixes (Flutter):
- Wrap multi-statement DB writes (insert/update/delete note, deleteDocument,
  deletePageData, OCR FTS merge, migrations) in transactions to prevent data
  loss on interruption and a read-modify-write FTS race.
- Fix PdfDocument leaks on exception (try/finally dispose) and preserve image
  aspect ratio when stamping images onto PDF pages.
- Guard file-picker against empty selection (was .single -> crash).
- Fix eraser ConcurrentModificationError and unmodifiable-list crash on PDF
  pages; capture page synchronously on save to stop wrong-page data loss.
- Fix Riverpod DB-not-ready races, broken pull-to-refresh, settings load race,
  and search N+1; transform stored annotations on PDF page rotation.
- Normalize pen pressure for devices without a pressure range.
- PPT: single source of truth for slide strokes so ink displays and exports.

UI/UX:
- Material 3 typography, theme-aware colors (dark-mode fixes), hover cursors
  and right-click/visible actions on desktop, keyboard shortcuts (undo/redo/
  save/find), toolbar overflow handling, friendlier empty states, semantic OCR
  status badges, relative timestamps, 1-based page indicators, large-deck PPT
  navigation, and a scratchpad-scope label in split view.

Server (optional backend):
- Persist JWT secret (was per-process random), block path traversal in storage,
  fix CORS '*'+credentials, add OCR job ownership checks, last-writer-wins sync
  guard, constant-time login, and split out heavy OCR deps so the API/tests run
  without them.

CI: Gitea workflows for format+analyze+test (Linux, system sqlite) and a
Windows release build; pristine `flutter analyze`, all Flutter and server tests
green.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

server/tests/conftest.py

@@ -0,0 +1,43 @@
+"""Shared test fixtures for BadNote tests."""
+
+import os
+import shutil
+import sys
+import tempfile
+
+import pytest
+import pytest_asyncio
+from httpx import ASGITransport, AsyncClient
+
+# Ensure the server package is importable
+sys.path.insert(0, os.path.join(os.path.dirname(__file__), ".."))
+
+os.environ["BADNOTE_STORAGE_PATH"] = "/tmp/badnote_test_storage"
+os.environ["BADNOTE_QUEUE_PATH"] = "/tmp/badnote_test_queue"
+os.environ["BADNOTE_JWT_SECRET"] = "test-secret-key-for-testing-only"
+
+from badnote_server.config import settings  # noqa: E402
+from badnote_server.main import app  # noqa: E402
+from badnote_server.database import get_db, close_db, init_db  # noqa: E402
+
+
+@pytest_asyncio.fixture(autouse=True)
+async def setup_db(tmp_path):
+    """Fresh DB and clean queue for each test."""
+    db_path = str(tmp_path / "test.db")
+    settings.db_path = db_path
+    # Clean the queue directory before each test
+    queue_path = settings.queue_path
+    if os.path.exists(queue_path):
+        shutil.rmtree(queue_path)
+    await init_db()
+    yield
+    await close_db()
+
+
+@pytest_asyncio.fixture
+async def client():
+    """Async test client for the FastAPI app."""
+    transport = ASGITransport(app=app)
+    async with AsyncClient(transport=transport, base_url="http://test") as ac:
+        yield ac