Full-CRUD sweep: update endpoints for tree, source, citation, relationship, media

Closes the rule #8 gap at the API layer: PATCH endpoints + service updates for Tree (name/description/visibility), Source, Citation (page/detail/confidence), Relationship (qualifier/notes), and Media (title/attachment) — editor-gated and audited. Every core entity now has create/read/update/delete. Edit UIs for these land in the frontend batch. 37 tests pass.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Signed-off-by: Justin Paul <justin@jpaul.me>

backend/app/schemas/tree.py

@@ -12,6 +12,12 @@ class TreeCreate(BaseModel):
     visibility: TreeVisibility = TreeVisibility.private
 
 
+class TreeUpdate(BaseModel):
+    name: str | None = None
+    description: str | None = None
+    visibility: TreeVisibility | None = None
+
+
 class TreeRead(BaseModel):
     model_config = ConfigDict(from_attributes=True)