Add a global search, and stop the sidebar logo squeezing

`GET /api/v1/search/` hands the client one flat index of everything worth
jumping to — flows and the nodes inside them, dashboards and the widgets on
them, panels, secrets, modules, workers and alert channels — and cmdk matches
it in the browser, so results narrow while typing without a round trip per
keystroke. A node hit is the one thing no list endpoint could answer: it opens
its flow with that node in focus.

The panel is reached from **Search** above Documentation in the sidebar, or
⌘K anywhere. The flow canvas palette moves to ⌘P, being the narrower of the two.

The panels dialog gains an address (`/dashboards?panels`) so a panel hit has
somewhere to land, and the sidebar logo gets `shrink-0`: the rail's width
animates while the logo is already back, and a flex item short of room is
squeezed rather than clipped.

docs/interface/index.md

@@ -22,8 +22,20 @@ phone the sidebar collapses to a sheet.
 | **Modules** | the Python packages your node code may import |
 | **Alerts** | where failures get sent |
 | **Admin** | users (superusers only) |
+| **Search** | anything in this installation, by name |
 | **Settings** | your account, appearance, and remote access |
 
+### Search
+
+**Search** at the foot of the sidebar, or ⌘K / Ctrl-K from anywhere, opens a
+panel that finds things by name as you type: flows and the nodes inside them,
+dashboards and the widgets on them, panels, secrets, modules, workers and alert
+channels. Picking a node opens its flow with that node in focus; picking a
+widget opens its dashboard.
+
+It searches this installation. Reached through a portal, other installations
+are behind **All installations** at the top of the sidebar.
+
 ## Home
 
 The one screen you leave open. Four things share it.