feat: configurable edge line style + width per type and per edge

Edge render (solid/dashed/dotted) and stroke width were hardcoded per
edge type. Expose both as user settings.

- Custom Style modal (Edges): line-style buttons, 1-4x width slider,
  live preview; left-list swatch renders the actual line.
- Per-edge EdgeModal: same controls; line style follows the type preset
  live until overridden.
- Renderer applies line_style/width_mult over BASE_STYLES (width scales
  markers + animation overlays); unset keeps the type default look.
- Persist line_style/width_mult through serializer, canvas save, and the
  edges API (new nullable columns, idempotent migration).

ha-relevant: yes

backend/app/db/database.py

@@ -85,6 +85,10 @@ async def init_db() -> None:
             await conn.exec_driver_sql("ALTER TABLE edges ADD COLUMN marker_start TEXT NOT NULL DEFAULT 'none'")
         with suppress(OperationalError):
             await conn.exec_driver_sql("ALTER TABLE edges ADD COLUMN marker_end TEXT NOT NULL DEFAULT 'none'")
+        with suppress(OperationalError):
+            await conn.exec_driver_sql("ALTER TABLE edges ADD COLUMN line_style TEXT")
+        with suppress(OperationalError):
+            await conn.exec_driver_sql("ALTER TABLE edges ADD COLUMN width_mult REAL")
         with suppress(OperationalError):
             await conn.exec_driver_sql("ALTER TABLE nodes ADD COLUMN cpu_count INTEGER")
         with suppress(OperationalError):

backend/app/db/models.py

@@ -85,6 +85,8 @@ class Edge(Base):
     speed: Mapped[str | None] = mapped_column(String)
     custom_color: Mapped[str | None] = mapped_column(String)
     path_style: Mapped[str | None] = mapped_column(String)
+    line_style: Mapped[str | None] = mapped_column(String)
+    width_mult: Mapped[float | None] = mapped_column(Float)
     animated: Mapped[str] = mapped_column(String, nullable=False, default='none')
     marker_start: Mapped[str] = mapped_column(String, nullable=False, default='none')
     marker_end: Mapped[str] = mapped_column(String, nullable=False, default='none')

backend/app/schemas/canvas.py

@@ -51,6 +51,8 @@ class EdgeSave(BaseModel):
     speed: str | None = None
     custom_color: str | None = None
     path_style: str | None = None
+    line_style: str | None = None
+    width_mult: float | None = None
     animated: str = 'none'
     marker_start: str = 'none'
     marker_end: str = 'none'

backend/app/schemas/edges.py

@@ -14,6 +14,8 @@ class EdgeBase(BaseModel):
     speed: str | None = None
     custom_color: str | None = None
     path_style: str | None = None
+    line_style: str | None = None
+    width_mult: float | None = None
     animated: str = 'none'
     marker_start: str = 'none'
     marker_end: str = 'none'
@@ -43,6 +45,8 @@ class EdgeUpdate(BaseModel):
     speed: str | None = None
     custom_color: str | None = None
     path_style: str | None = None
+    line_style: str | None = None
+    width_mult: float | None = None
     animated: str | None = None
     marker_start: str | None = None
     marker_end: str | None = None

backend/tests/test_canvas.py

@@ -62,6 +62,17 @@ async def test_save_canvas_round_trips_marker_shapes(client: AsyncClient, header
     assert edge["marker_end"] == "arrow"
 
 
+async def test_save_canvas_round_trips_line_style_and_width(client: AsyncClient, headers: dict):
+    n1 = node_payload(label="Router", type="router")
+    n2 = node_payload(label="Switch", type="switch")
+    e1 = edge_payload(n1["id"], n2["id"], type="wifi", line_style="dotted", width_mult=3)
+    await client.post("/api/v1/canvas/save", json={"nodes": [n1, n2], "edges": [e1], "viewport": {}}, headers=headers)
+
+    edge = (await client.get("/api/v1/canvas", headers=headers)).json()["edges"][0]
+    assert edge["line_style"] == "dotted"
+    assert edge["width_mult"] == 3
+
+
 async def test_save_canvas_coerces_legacy_boolean_marker(client: AsyncClient, headers: dict):
     n1 = node_payload(label="Router", type="router")
     n2 = node_payload(label="Switch", type="switch")

backend/tests/test_edges.py

@@ -91,6 +91,31 @@ async def test_update_edge_custom_color_and_path_style(client: AsyncClient, head
     assert res.json()["path_style"] == "smooth"
 
 
+async def test_create_edge_with_line_style_and_width(client: AsyncClient, headers: dict, two_nodes):
+    src, tgt = two_nodes
+    res = await client.post("/api/v1/edges", json={"source": src, "target": tgt, "type": "wifi", "line_style": "dotted", "width_mult": 3}, headers=headers)
+    assert res.status_code == 201
+    assert res.json()["line_style"] == "dotted"
+    assert res.json()["width_mult"] == 3
+
+
+async def test_update_edge_line_style_and_width(client: AsyncClient, headers: dict, two_nodes):
+    src, tgt = two_nodes
+    edge_id = (await client.post("/api/v1/edges", json={"source": src, "target": tgt, "type": "ethernet"}, headers=headers)).json()["id"]
+    res = await client.patch(f"/api/v1/edges/{edge_id}", json={"line_style": "dashed", "width_mult": 2}, headers=headers)
+    assert res.status_code == 200
+    assert res.json()["line_style"] == "dashed"
+    assert res.json()["width_mult"] == 2
+
+
+async def test_create_edge_defaults_line_style_none(client: AsyncClient, headers: dict, two_nodes):
+    src, tgt = two_nodes
+    res = await client.post("/api/v1/edges", json={"source": src, "target": tgt, "type": "ethernet"}, headers=headers)
+    assert res.status_code == 201
+    assert res.json()["line_style"] is None
+    assert res.json()["width_mult"] is None
+
+
 async def test_create_edge_with_marker_shapes(client: AsyncClient, headers: dict, two_nodes):
     src, tgt = two_nodes
     res = await client.post("/api/v1/edges", json={"source": src, "target": tgt, "type": "ethernet", "marker_start": "diamond", "marker_end": "arrow"}, headers=headers)