fix(ui): unify the four navigate views, add Set as target everywhere

Continuing the consistency pass: the four screens that show the
distance/bearing "navigate to a point" view (Nodes, Waypoints, Trail's
Track back, and navigating to a location shared in a message) had drifted
apart in three ways.

Only two of the four passed an EtaTracker to navview::draw(), so only
Nodes and Track back showed the closing-speed/ETA line -- navigating to a
waypoint or a shared location left it off for no reason. All four get one
now. They also left the view on three different key sets (Back alone,
Back+LEFT/RIGHT, Back+Enter); Back is now the only way out of any of them,
so a stray sideways nudge can't drop you out of a running track-back.
Messages' renderNav() also switched from reading node_prefs directly to
the shared useImperial() helper the other three already used.

Set as target -- the row Nodes and Waypoints both offer for a coordinate
-- was missing from the message-location Options menu; added alongside
Navigate and Save waypoint.

Nodes' own Set as target required a full 32-byte public key, which a
name-only live-track entry (someone sharing position on a channel who
isn't a saved contact -- the group-outing case this exists for) never
has. One flag was doing two jobs: "can be pinged" (needs the full key)
and "can be identified" (needs only the 6-byte prefix a person target
actually uses). Split into has_key/has_prefix; Set as target now only
needs a position, resolving to a person target (follows them) when a
prefix is available and a place target (pinned where they were) when it
isn't -- the same distinction Locator's own picker already draws.

Locator's target picker separately still listed the people pinned to the
Favourites Dial as its privileged top tier, which stopped making sense
once pinning and favouriting became separate concepts. It now leads with
favourites instead, matching every other list in the firmware.

docs/solo_features/message_screen/message_screen.md

@@ -64,7 +64,7 @@ Posting to a **room server** needs a login handshake — the device does this on
 
 Messages appear as chat bubbles sized to their content — **right**-anchored for outgoing, **left** for incoming — with sender name and a compact age indicator (`3m`, `2h`, `>1d`) in the top-right corner. List runs **newest at the bottom**; opening a history starts at the latest message, scrolling up goes further back.
 
-**Short Enter** on a message opens it in fullscreen. **Hold Enter** — on a history row or in fullscreen — opens the same options menu: Reply, plus **Navigate** / **Save waypoint** when the message contains a location, and **Path** / **Relayed by** when hop data is available (see Fullscreen message view). You don't need to open the message first.
+**Short Enter** on a message opens it in fullscreen. **Hold Enter** — on a history row or in fullscreen — opens the same options menu: Reply, plus **Navigate** / **Save waypoint** / **Set as target** when the message contains a location, and **Path** / **Relayed by** when hop data is available (see Fullscreen message view). You don't need to open the message first.
 
 ---
 
@@ -82,10 +82,11 @@ If the message is a reply addressed to someone (`@[nick]`), a **To: nick** bar i
 | :-----------------------: | :-----------------------: |
 | ![](./fullscreen_menu_oled.png) | ![](./fullscreen_menu_eink.png) |
 
-**Hold Enter** in fullscreen opens the options menu. It always offers **Reply** for an incoming message, and when the message contains a **location** it adds two more:
+**Hold Enter** in fullscreen opens the options menu. It always offers **Reply** for an incoming message, and when the message contains a **location** it adds three more:
 
 - **Navigate** — opens the bearing/distance view to those coordinates (the same two-bearing screen as Waypoints and Nearby; **Back** returns to the message).
 - **Save waypoint** — stores the location as a waypoint (visible on the trail map and in the Waypoints list).
+- **Set as target** — pins those coordinates as the active **Locator/Nav target** in one step, the same row Nodes and Waypoints offer (see Tools › Locator).
 
 A location is any `lat,lon` pair in the text — exactly what the `{loc}` placeholder inserts — so you can navigate to anything a contact shares. A `[WAY]lat,lon label` share also carries a name, used as the waypoint label. This works on DMs and channel messages, incoming or outgoing.