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>

lib/screens/pdf_text_search.dart

@@ -0,0 +1,141 @@
+import 'package:flutter/material.dart';
+import 'package:syncfusion_flutter_pdfviewer/pdfviewer.dart';
+
+/// A dialog for searching text within a PDF using SfPdfViewer's built-in search.
+class PdfTextSearchDialog extends StatefulWidget {
+  final PdfViewerController viewerController;
+
+  const PdfTextSearchDialog({super.key, required this.viewerController});
+
+  @override
+  State<PdfTextSearchDialog> createState() => _PdfTextSearchDialogState();
+}
+
+class _PdfTextSearchDialogState extends State<PdfTextSearchDialog> {
+  final TextEditingController _queryController = TextEditingController();
+  PdfTextSearchResult? _searchResult;
+  String _statusText = '';
+
+  @override
+  void dispose() {
+    _queryController.dispose();
+    _searchResult?.clear();
+    super.dispose();
+  }
+
+  void _search() {
+    final query = _queryController.text.trim();
+    if (query.isEmpty) return;
+
+    final result = widget.viewerController.searchText(query);
+    setState(() {
+      _searchResult = result;
+      _updateStatus();
+    });
+  }
+
+  void _nextMatch() {
+    _searchResult?.nextInstance();
+    _updateStatus();
+  }
+
+  void _previousMatch() {
+    _searchResult?.previousInstance();
+    _updateStatus();
+  }
+
+  void _updateStatus() {
+    final result = _searchResult;
+    if (result == null || result.totalInstanceCount == 0) {
+      setState(() => _statusText = 'No matches');
+    } else {
+      setState(() {
+        _statusText =
+            '${result.currentInstanceIndex} of ${result.totalInstanceCount} matches';
+      });
+    }
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    return Dialog(
+      child: ConstrainedBox(
+        constraints: const BoxConstraints(maxWidth: 400),
+        child: Padding(
+          padding: const EdgeInsets.all(16),
+          child: Column(
+            mainAxisSize: MainAxisSize.min,
+            children: [
+              Row(
+                children: [
+                  Expanded(
+                    child: TextField(
+                      controller: _queryController,
+                      autofocus: true,
+                      decoration: const InputDecoration(
+                        hintText: 'Search in PDF...',
+                        prefixIcon: Icon(Icons.search),
+                        isDense: true,
+                        border: OutlineInputBorder(),
+                      ),
+                      onSubmitted: (_) => _search(),
+                    ),
+                  ),
+                  const SizedBox(width: 8),
+                  IconButton(
+                    icon: const Icon(Icons.search),
+                    tooltip: 'Search',
+                    onPressed: _search,
+                  ),
+                ],
+              ),
+              const SizedBox(height: 12),
+              Row(
+                children: [
+                  Text(
+                    _statusText,
+                    style: Theme.of(context).textTheme.bodySmall,
+                  ),
+                  const Spacer(),
+                  IconButton(
+                    icon: const Icon(Icons.keyboard_arrow_up),
+                    tooltip: 'Previous match',
+                    onPressed:
+                        _searchResult != null &&
+                            _searchResult!.totalInstanceCount > 0
+                        ? _previousMatch
+                        : null,
+                    iconSize: 20,
+                  ),
+                  IconButton(
+                    icon: const Icon(Icons.keyboard_arrow_down),
+                    tooltip: 'Next match',
+                    onPressed:
+                        _searchResult != null &&
+                            _searchResult!.totalInstanceCount > 0
+                        ? _nextMatch
+                        : null,
+                    iconSize: 20,
+                  ),
+                  IconButton(
+                    icon: const Icon(Icons.close),
+                    tooltip: 'Clear search',
+                    onPressed: () {
+                      _searchResult?.clear();
+                      setState(() {
+                        _queryController.clear();
+                        _searchResult = null;
+                        _statusText = '';
+                      });
+                    },
+                    iconSize: 20,
+                  ),
+                ],
+              ),
+            ],
+          ),
+        ),
+      ),
+    );
+  }
+}