feat: add admin panel at /admin for full dashboard configuration

- Backend: ConfigManager write methods (atomic YAML save), admin CRUD
  router for settings (display/odoo/refresh) and nodes, WS broadcast
  on config changes, fix nmap scan blocking event loop with to_thread
- Frontend: admin UI with tab navigation, overview dashboard, node
  CRUD table with modal form, Odoo/display/refresh settings pages,
  typed API wrappers, active views filtering, config_changed WS handler
- Infra: nginx no-cache headers for HTML, cache-forever for hashed assets
- Fixes: WebSocket reconnect loop (ref pattern), rotation index OOB
  when views shrink, mutable node list cache

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

backend/routers/admin.py

@@ -0,0 +1,121 @@
+from fastapi import APIRouter, HTTPException
+from pydantic import BaseModel
+
+from modules.config_manager import ConfigManager
+from routers.ws import broadcast
+
+router = APIRouter(prefix="/api/admin", tags=["admin"])
+
+# Will be set from main.py
+config: ConfigManager = None  # type: ignore
+
+
+def init(cfg: ConfigManager) -> None:
+    global config
+    config = cfg
+
+
+# ── Pydantic models ─────────────────────────────────────────
+
+class DisplaySettings(BaseModel):
+    resolution: str | None = None
+    rotation_interval_seconds: int | None = None
+    transition: str | None = None
+    theme: str | None = None
+    active_views: list[str] | None = None
+
+
+class OdooSettings(BaseModel):
+    url: str | None = None
+    database: str | None = None
+    username: str | None = None
+    password: str | None = None
+    exclude_company_ids: list[int] | None = None
+
+
+class RefreshSettings(BaseModel):
+    odoo_minutes: int | None = None
+    network_minutes: int | None = None
+    ping_seconds: int | None = None
+
+
+class NodeModel(BaseModel):
+    name: str
+    ip: str
+    username: str | None = None
+    password: str | None = None
+    public_url: str | None = None
+    icon: str = "device"
+    type: str | None = None
+    parent: str | None = None
+    connections: list[str] = []
+
+
+# ── Settings endpoints ──────────────────────────────────────
+
+@router.get("/settings")
+async def get_settings():
+    return config.get_settings()
+
+
+@router.put("/settings/display")
+async def update_display(body: DisplaySettings):
+    values = body.model_dump(exclude_none=True)
+    result = config.update_settings("display", values)
+    await broadcast("config_changed", {"section": "display"})
+    return result
+
+
+@router.put("/settings/odoo")
+async def update_odoo(body: OdooSettings):
+    values = body.model_dump(exclude_none=True)
+    result = config.update_settings("odoo", values)
+    await broadcast("config_changed", {"section": "odoo"})
+    return result
+
+
+@router.put("/settings/refresh")
+async def update_refresh(body: RefreshSettings):
+    values = body.model_dump(exclude_none=True)
+    result = config.update_settings("refresh", values)
+    await broadcast("config_changed", {"section": "refresh"})
+    return result
+
+
+# ── Node endpoints ──────────────────────────────────────────
+
+@router.get("/nodes")
+async def get_nodes():
+    return config.get_nodes()
+
+
+@router.post("/nodes", status_code=201)
+async def add_node(body: NodeModel):
+    nodes = config.get_nodes()
+    for n in nodes:
+        if n["ip"] == body.ip:
+            raise HTTPException(400, f"Node with IP {body.ip} already exists")
+    nodes.append(body.model_dump(exclude_none=True))
+    config.save_nodes(nodes)
+    await broadcast("config_changed", {"section": "nodes"})
+    return body.model_dump(exclude_none=True)
+
+
+@router.put("/nodes")
+async def replace_nodes(body: list[NodeModel]):
+    nodes = [n.model_dump(exclude_none=True) for n in body]
+    config.save_nodes(nodes)
+    await broadcast("config_changed", {"section": "nodes"})
+    return nodes
+
+
+@router.delete("/nodes/{ip}")
+async def delete_node(ip: str):
+    nodes = config.get_nodes()
+    original_len = len(nodes)
+    nodes = [n for n in nodes if n.get("ip") != ip]
+    if len(nodes) == original_len:
+        raise HTTPException(404, f"Node with IP {ip} not found")
+    config.save_nodes(nodes)
+    await broadcast("config_changed", {"section": "nodes"})
+    return {"deleted": ip}