Add Projects: third tab, swipe-to-file, per-project note capture

Notes gain an optional project (schema v4, additive). Projects derive
from note values like tags — no separate entity. Tab naming
(Projects/Categories) is a Settings choice applied across the UI.

Claude-Session: https://claude.ai/code/session_014esDWi42URLEC6Cj17hGQ3

Notes/Model/NoteMapper.swift

@@ -31,6 +31,7 @@ enum NoteMapper {
         entity.text = note.payload.text
         entity.sourceRaw = note.payload.source.rawValue
         entity.tags = note.payload.tags
+        entity.project = note.payload.project
         entity.createdAt = note.meta.createdAt
         entity.modifiedAt = note.meta.modifiedAt
         entity.jsonRelativePath = relativePath
@@ -54,7 +55,8 @@ enum NoteMapper {
                 source: entity.source,
                 tags: entity.tags,
                 context: entity.context,
-                audio: entity.audio
+                audio: entity.audio,
+                project: entity.project
             )
         )
     }