feat(ui): Flows page (5th destination) + keyboard shortcuts

Two operator-DX additions:

1. **Flows** is the new third destination in the sidebar.
   Lists saved flows from the hub via the new HubAdmin
   ListFlows RPC. Each row has a Run button that opens an
   input dialog (key=value pairs, one per line, all values
   sent as text payloads — the binary-input case stays in
   `fai run` CLI). Flow runs in a non-dismissable progress
   dialog; output is shown per-key with monospace
   selectable text. Errors render with the exception detail
   for diagnosis.

2. **Keyboard shortcuts** at the shell level:
   - Cmd+1 / Cmd+2 / Cmd+3 / Cmd+4 / Cmd+5 jump to the
     matching destination (Doctor / Modules / Flows / Audit
     / Approvals).
   - Cmd+, opens the Settings dialog (macOS convention).

   Implemented via Flutter's Shortcuts/Actions/Intent triple
   so the bindings are discoverable in IDE devtools and
   composable with platform-specific overrides later.

Bumps fai_studio 0.7.3 -> 0.8.0.

Signed-off-by: flemming-it <stefan.a.flemming@googlemail.com>

pubspec.yaml

@@ -1,7 +1,7 @@
 name: fai_studio
 description: "F∆I Studio — desktop GUI for the F∆I hub"
 publish_to: 'none'
-version: 0.7.3
+version: 0.8.0
 
 environment:
   sdk: ^3.11.0-200.1.beta