feat: show inventory timestamps on Device Inventory tiles

Surface the same lifecycle timestamps on the Device Inventory cards as on the
detail panel. Tiles for devices placed on a canvas show their linked node's
created / last scan / last modified / last seen (correlated by ip or
ieee_address, aggregated across matches: created = oldest, others = newest).
Devices not yet on any canvas fall back to their discovered_at.

Rendered as compact relative times ("2d ago") with the full date on hover, in
a tight two-column footer so the tile keeps its original footprint.

Backend: PendingDeviceResponse gains node_created_at / node_last_scan /
node_last_modified / node_last_seen; the canvas correlation now also pulls node
timestamps in the same single query. Frontend: shared timeFormat util
(absolute + relative), reused by the detail panel.

ha-relevant: maybe

backend/app/api/routes/scan.py

@@ -1,6 +1,7 @@
 import ipaddress
 import logging
 import uuid
+from datetime import datetime
 from typing import Any
 
 from fastapi import APIRouter, BackgroundTasks, Depends, HTTPException
@@ -193,51 +194,80 @@ async def stop_scan(
     return {"stopping": True}
 
 
-async def _canvas_counts(
-    db: AsyncSession, devices: list[PendingDevice]
-) -> dict[str, int]:
-    """Map each device id → number of distinct canvases (designs) it appears on.
+def _agg(values: list[datetime], *, newest: bool) -> datetime | None:
+    """Pick the newest (max) or oldest (min) of a list of timestamps, or None."""
+    present = [v for v in values if v is not None]
+    if not present:
+        return None
+    return max(present) if newest else min(present)
 
-    Correlates a scanned device to existing nodes by ``ieee_address`` (exact) or
-    ``ip`` (exact). Runs a single node query and groups in Python — node counts are
-    small for a homelab, so this avoids an N+1 per device.
+
+async def _canvas_correlation(
+    db: AsyncSession, devices: list[PendingDevice]
+) -> dict[str, dict[str, Any]]:
+    """Correlate each device to existing canvas nodes by ``ieee_address`` or ``ip``.
+
+    Returns, per device id: the number of distinct canvases (designs) it appears
+    on, plus aggregated timestamps from every matching node — created_at (oldest),
+    last_scan / updated_at / last_seen (newest). One node query, grouped in Python
+    (node counts are small for a homelab), so no N+1 per device.
     """
     if not devices:
         return {}
     rows = (
         await db.execute(
-            select(Node.ip, Node.ieee_address, Node.design_id).where(
-                Node.design_id.isnot(None)
-            )
+            select(
+                Node.ip,
+                Node.ieee_address,
+                Node.design_id,
+                Node.created_at,
+                Node.last_scan,
+                Node.updated_at,
+                Node.last_seen,
+            ).where(Node.design_id.isnot(None))
         )
     ).all()
-    # ip → set(design_id), ieee → set(design_id)
-    by_ip: dict[str, set[str]] = {}
-    by_ieee: dict[str, set[str]] = {}
-    for ip, ieee, design_id in rows:
-        if ip:
-            by_ip.setdefault(ip, set()).add(design_id)
-        if ieee:
-            by_ieee.setdefault(ieee, set()).add(design_id)
+    # Index matching nodes by ip and by ieee so a device can look up both.
+    by_ip: dict[str, list[Any]] = {}
+    by_ieee: dict[str, list[Any]] = {}
+    for row in rows:
+        if row.ip:
+            by_ip.setdefault(row.ip, []).append(row)
+        if row.ieee_address:
+            by_ieee.setdefault(row.ieee_address, []).append(row)
 
-    counts: dict[str, int] = {}
+    info: dict[str, dict[str, Any]] = {}
     for d in devices:
-        designs: set[str] = set()
+        matched = []
         if d.ieee_address:
-            designs |= by_ieee.get(d.ieee_address, set())
+            matched += by_ieee.get(d.ieee_address, [])
         if d.ip:
-            designs |= by_ip.get(d.ip, set())
-        counts[d.id] = len(designs)
-    return counts
+            matched += by_ip.get(d.ip, [])
+        # De-duplicate nodes matched by both ip and ieee.
+        matched = list({id(m): m for m in matched}.values())
+        designs = {m.design_id for m in matched}
+        info[d.id] = {
+            "canvas_count": len(designs),
+            "node_created_at": _agg([m.created_at for m in matched], newest=False),
+            "node_last_scan": _agg([m.last_scan for m in matched], newest=True),
+            "node_last_modified": _agg([m.updated_at for m in matched], newest=True),
+            "node_last_seen": _agg([m.last_seen for m in matched], newest=True),
+        }
+    return info
 
 
 async def _with_canvas_counts(
     db: AsyncSession, devices: list[PendingDevice]
 ) -> list[PendingDevice]:
-    """Attach a transient ``canvas_count`` to each device for the response schema."""
-    counts = await _canvas_counts(db, devices)
+    """Attach transient canvas count + linked-node timestamps for the response."""
+    info = await _canvas_correlation(db, devices)
     for d in devices:
-        d.canvas_count = counts.get(d.id, 0)
+        meta = info.get(d.id, {})
+        d.canvas_count = meta.get("canvas_count", 0)
+        d.node_created_at = meta.get("node_created_at")
+        d.node_last_scan = meta.get("node_last_scan")
+        d.node_last_modified = meta.get("node_last_modified")
+        d.node_last_seen = meta.get("node_last_seen")
     return devices
 
 

backend/app/schemas/scan.py

@@ -24,6 +24,13 @@ class PendingDeviceResponse(BaseModel):
     # Number of distinct canvases (designs) this device already appears on,
     # correlated by ip / ieee_address against existing nodes. Computed per-request.
     canvas_count: int = 0
+    # Timestamps from the linked canvas node(s), correlated by ip / ieee_address.
+    # Null when the device is not on any canvas yet. Aggregated across matches:
+    # created_at = oldest; last_scan / last_modified / last_seen = newest.
+    node_created_at: datetime | None = None
+    node_last_scan: datetime | None = None
+    node_last_modified: datetime | None = None
+    node_last_seen: datetime | None = None
 
     model_config = {"from_attributes": True}