feat: add custom style theme with per-type node/edge style editor

- New 'custom' ThemeId with dedicated ThemeCard + pencil edit button
- CustomStyleModal: two-column editor for all node types (excl. groupRect/group) and edge types
  - Per node: border, background, icon color + opacity, default size (w/h)
  - Per edge: color + opacity, path style, animation
  - 'Apply to existing [Type]' per type, 'Apply All to Canvas' footer action
- canvasStore: applyTypeNodeStyle, applyTypeEdgeStyle, applyAllCustomStyles actions
- themeStore: customStyle state + setCustomStyle action
- Backend: custom_style JSON column on canvas_state (ALTER TABLE migration), saved/loaded with canvas
- App.tsx: custom_style included in save payload, restored on load (API + standalone)
- Tests: +8 frontend (themeStore + canvasStore), +3 backend (canvas API)

backend/app/api/routes/canvas.py

@@ -25,6 +25,7 @@ async def load_canvas(db: AsyncSession = Depends(get_db), _: str = Depends(get_c
         nodes=[NodeResponse.model_validate(n) for n in nodes],
         edges=[EdgeResponse.model_validate(e) for e in edges],
         viewport=viewport,
+        custom_style=state.custom_style if state else None,
     )
 
 
@@ -67,13 +68,14 @@ async def save_canvas(
         else:
             db.add(Edge(**edge_data.model_dump()))
 
-    # Upsert viewport
+    # Upsert viewport + custom style
     state = await db.get(CanvasState, 1)
     if state:
         state.viewport = body.viewport
+        state.custom_style = body.custom_style
         state.saved_at = datetime.now(timezone.utc)
     else:
-        db.add(CanvasState(id=1, viewport=body.viewport))
+        db.add(CanvasState(id=1, viewport=body.viewport, custom_style=body.custom_style))
 
     await db.commit()
     return {"saved": True}

backend/app/db/database.py

@@ -84,6 +84,8 @@ async def init_db() -> None:
             await conn.exec_driver_sql("ALTER TABLE edges ADD COLUMN waypoints JSON")
         with suppress(OperationalError):
             await conn.exec_driver_sql("ALTER TABLE nodes ADD COLUMN properties JSON")
+        with suppress(OperationalError):
+            await conn.exec_driver_sql("ALTER TABLE canvas_state ADD COLUMN custom_style JSON")
         # Migrate hardware columns → properties JSON (idempotent: only runs on nodes where properties IS NULL)
         with suppress(OperationalError):
             rows = await conn.exec_driver_sql(

backend/app/db/models.py

@@ -78,6 +78,7 @@ class CanvasState(Base):
 
     id: Mapped[int] = mapped_column(Integer, primary_key=True, default=1)
     viewport: Mapped[dict[str, Any]] = mapped_column(JSON, default=dict)
+    custom_style: Mapped[dict[str, Any] | None] = mapped_column(JSON, nullable=True)
     saved_at: Mapped[datetime] = mapped_column(DateTime(timezone=True), default=_now)
 
 

backend/app/schemas/canvas.py

@@ -62,9 +62,11 @@ class CanvasSaveRequest(BaseModel):
     nodes: list[NodeSave] = []
     edges: list[EdgeSave] = []
     viewport: dict[str, Any] = {}
+    custom_style: dict[str, Any] | None = None
 
 
 class CanvasStateResponse(BaseModel):
     nodes: list[NodeResponse]
     edges: list[EdgeResponse]
     viewport: dict[str, Any]
+    custom_style: dict[str, Any] | None = None

backend/tests/test_canvas.py

@@ -557,3 +557,42 @@ async def test_save_canvas_edge_update_existing(client: AsyncClient, headers: di
     edge = canvas["edges"][0]
     assert edge["label"] == "updated"
     assert edge["custom_color"] == "#ff0000"
+
+
+# ── custom_style ──────────────────────────────────────────────────────────────
+
+async def test_save_and_load_custom_style(client: AsyncClient, headers: dict):
+    custom_style = {
+        "nodes": {
+            "server": {"borderColor": "#ff0000", "borderOpacity": 0.8, "bgColor": "#000000", "bgOpacity": 1, "iconColor": "#ff0000", "iconOpacity": 1, "width": 200, "height": 80},
+        },
+        "edges": {
+            "ethernet": {"color": "#00ff00", "opacity": 1, "pathStyle": "bezier", "animated": "none"},
+        },
+    }
+    payload = {"nodes": [], "edges": [], "viewport": {"theme_id": "custom"}, "custom_style": custom_style}
+    res = await client.post("/api/v1/canvas/save", json=payload, headers=headers)
+    assert res.status_code == 200
+
+    canvas = (await client.get("/api/v1/canvas", headers=headers)).json()
+    assert canvas["custom_style"] is not None
+    assert canvas["custom_style"]["nodes"]["server"]["borderColor"] == "#ff0000"
+    assert canvas["custom_style"]["edges"]["ethernet"]["color"] == "#00ff00"
+
+
+async def test_load_canvas_custom_style_null_by_default(client: AsyncClient, headers: dict):
+    res = await client.get("/api/v1/canvas", headers=headers)
+    assert res.status_code == 200
+    assert res.json()["custom_style"] is None
+
+
+async def test_save_canvas_custom_style_overwrite(client: AsyncClient, headers: dict):
+    style_v1 = {"nodes": {"server": {"borderColor": "#aabbcc", "borderOpacity": 1, "bgColor": "#000000", "bgOpacity": 1, "iconColor": "#aabbcc", "iconOpacity": 1, "width": 0, "height": 0}}, "edges": {}}
+    style_v2 = {"nodes": {"proxmox": {"borderColor": "#ff6e00", "borderOpacity": 1, "bgColor": "#111111", "bgOpacity": 1, "iconColor": "#ff6e00", "iconOpacity": 1, "width": 0, "height": 0}}, "edges": {}}
+
+    await client.post("/api/v1/canvas/save", json={"nodes": [], "edges": [], "viewport": {}, "custom_style": style_v1}, headers=headers)
+    await client.post("/api/v1/canvas/save", json={"nodes": [], "edges": [], "viewport": {}, "custom_style": style_v2}, headers=headers)
+
+    canvas = (await client.get("/api/v1/canvas", headers=headers)).json()
+    assert "proxmox" in canvas["custom_style"]["nodes"]
+    assert "server" not in canvas["custom_style"]["nodes"]