Add SwiftData-backed image support

[adamrdrew]

Motivation

• Add first-class image support stored in SwiftData (CloudKit-backed) and addressable via takenote://image/<UUID> URLs for markdown preview and sharing.
• Support user workflow of dragging an OS-supported image into a note to ingest it and insert a markdown image link, and ensure images are removed when no notes reference them.

Description

• Introduce new SwiftData models NoteImage and NoteImageLink where NoteImage stores image bytes with @Attribute(.externalStorage), a mimeType, a uuid, and a referenceCount for simple garbage collection. (TakeNote/Models/NoteImage.swift, TakeNote/Models/NoteImageLink.swift).
• Add @Relationship var imageLinks: [NoteImageLink]? to Note to track references from notes (model changes added to the app ModelContainer). (TakeNote/Models/Note.swift, TakeNote/TakeNoteApp.swift).
• Implement NoteImageManager with ingestImage(from:note:), updateImageLinks(for:), and removeImageLinks(for:) to ingest files, parse takenote://image/<UUID> links, maintain reference counts, and delete unreferenced images. (TakeNote/Library/NoteImageManager.swift).
• Register a custom URL protocol TakeNoteImageURLProtocol that serves image bytes for takenote://image/<UUID> requests by fetching the NoteImage from the SwiftData container; hook registration into app init via TakeNoteImageURLProtocolRegistrar.registerIfNeeded(container:). (TakeNote/Library/TakeNoteImageURLProtocol.swift, TakeNote/TakeNoteApp.swift).
• Wire drag-and-drop image handling into the editor by adding a dropDestination(for: URL.self) and handleImageDrop which calls NoteImageManager.ingestImage and inserts ![](<takenote://image/UUID>) markdown links at caret or appended in preview. (TakeNote/Views/NoteEditor/NoteEditor.swift).
• Ensure image link bookkeeping is updated when notes are processed (e.g. selection changes) via NoteImageManager.updateImageLinks and when notes are emptied from trash via NoteImageManager.removeImageLinks. (TakeNote/Views/NoteList/NoteList.swift, TakeNote/TakeNoteVM.swift).
• Include the new models in the dev CloudKit bootstrap configuration and bump ckBootstrapVersionCurrent so the Dev schema can be updated. (TakeNote/TakeNoteApp.swift).

Testing

• No automated tests were run against these changes.

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Codex Task