Fix browser media drag and drop handling

Add a shared DragPasteboardMedia importer for file URLs, file promises, and direct pasteboard media data from browser drags.

Use the shared importer from Article List, Quick Post, Quick Share, and Writer so Chrome and x.com image drops follow the same code path.

Prevent text editors from inserting browser drag placeholder text such as Image when the drop actually contains importable media.

Make pasteboard media import more resilient by falling back from file URLs to raw item data, trying alternate media flavors after conversion failures, parsing file URL item representations more broadly, and avoiding duplicate imports when a file URL import already succeeded.

Register DragPasteboardMedia.swift in the Xcode project and verify the Planet macOS Debug build with CODE_SIGNING_ALLOWED=NO.

Author: livid

Planet.xcodeproj/project.pbxproj

@@ -506,6 +506,7 @@
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 		6AFCF7E72B737371002299BA /* TemplateMonitor.swift in Sources */ = {isa = PBXBuildFile; fileRef = 2AC889412B71D4200090D355 /* TemplateMonitor.swift */; };
+		6B50625D6A91C63998683BCA /* DragPasteboardMedia.swift in Sources */ = {isa = PBXBuildFile; fileRef = 2F4FA3B2D9A523EB833A02F3 /* DragPasteboardMedia.swift */; };
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@@ -552,6 +553,7 @@
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 		A14E34849B8C45E69780141C /* SearchDatabase.swift in Sources */ = {isa = PBXBuildFile; fileRef = CB6EC2B7EEF3EF83DA342363 /* SearchDatabase.swift */; };
 		A8E3461C94DD9CF45659CC72 /* PlanetAIChatSessionsView.swift in Sources */ = {isa = PBXBuildFile; fileRef = 4C06A60D631FAB5EEF3BAF8C /* PlanetAIChatSessionsView.swift */; };
+		B1554926223D7E6D8B65E40D /* DragPasteboardMedia.swift in Sources */ = {isa = PBXBuildFile; fileRef = 2F4FA3B2D9A523EB833A02F3 /* DragPasteboardMedia.swift */; };
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@@ -788,6 +790,7 @@
 		2AFB897529BA3ED8003D893E /* PlanetKeyManagerModel.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = PlanetKeyManagerModel.swift; sourceTree = "<group>"; };
 		2AFFD51A28AD760400EDB020 /* HelpLinkButton.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = HelpLinkButton.swift; sourceTree = "<group>"; };
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+		2F4FA3B2D9A523EB833A02F3 /* DragPasteboardMedia.swift */ = {isa = PBXFileReference; includeInIndex = 1; lastKnownFileType = sourcecode.swift; path = DragPasteboardMedia.swift; sourceTree = "<group>"; };
 		342A67E3EAD082AA10974830 /* NaturalLanguage.framework */ = {isa = PBXFileReference; includeInIndex = 1; lastKnownFileType = wrapper.framework; name = NaturalLanguage.framework; path = System/Library/Frameworks/NaturalLanguage.framework; sourceTree = SDKROOT; };
 		3BF7A284CCD68E7CBE9F9D73 /* fi */ = {isa = PBXFileReference; includeInIndex = 1; lastKnownFileType = text.plist.strings; name = fi; path = fi.lproj/InfoPlist.strings; sourceTree = "<group>"; };
 		412635EFFFDD8D11BBC4BC56 /* ThemeColorExtractor.swift */ = {isa = PBXFileReference; includeInIndex = 1; lastKnownFileType = sourcecode.swift; path = ThemeColorExtractor.swift; sourceTree = "<group>"; };
@@ -1363,6 +1366,7 @@
 				C1A2B3D4E5F6A7B8C9D0E1F2 /* SleepPreventer.swift */,
 				03E9DC5C055F824D215A8981 /* MarkdownEditorTextView.swift */,
 				412635EFFFDD8D11BBC4BC56 /* ThemeColorExtractor.swift */,
+				2F4FA3B2D9A523EB833A02F3 /* DragPasteboardMedia.swift */,
 			);
 			path = Helper;
 			sourceTree = "<group>";
@@ -2270,6 +2274,7 @@
 				C1A2B3D4E5F6A7B8C9D0E1F3 /* SleepPreventer.swift in Sources */,
 				6AADD6C72AF8809600898A6E /* MyArticleModel+SavePublic.swift in Sources */,
 				BF9F577F9FFA8A77F474CF1A /* PlanetStore+Spotlight.swift in Sources */,
+				6B50625D6A91C63998683BCA /* DragPasteboardMedia.swift in Sources */,
 			);
 			runOnlyForDeploymentPostprocessing = 0;
 		};
@@ -2517,6 +2522,7 @@
 				B2B22802B0B767E09FE903A2 /* ArticleSpeechPlayer.swift in Sources */,
 				9F1807DD072155243C041DFC /* ThemeColorExtractor.swift in Sources */,
 				8F03F9FAEFE88AA819E13F28 /* FeatureFlags.swift in Sources */,
+				B1554926223D7E6D8B65E40D /* DragPasteboardMedia.swift in Sources */,
 			);
 			runOnlyForDeploymentPostprocessing = 0;
 		};