Journal UI: write and read season notes where you're already looking (#53)

happens. Notes get written standing in the garden holding a phone, usually
one-handed — if it takes more than a couple of taps from looking at a bed to
typing a sentence, the log stays empty.

So the journal is a tab in the rail #49 settled, and selecting a bed puts a
"📝 Add note" button in the inspector that scopes the journal to that bed and
switches to it. The composer is already open in there rather than behind an
"add" button, which makes it two taps from a selected bed to typing.

The observed date defaults to today in the VIEWER's timezone, not UTC — "today"
means the day you are standing in the garden — and stays editable, because you
write up Saturday's observations on Sunday.

Discoverability is the other half. A log you have to remember exists is a log
nobody reads, so the inspector button carries the note count for that bed and
the Journal tab carries the garden's total: a garden with a season's notes in it
no longer looks identical to an empty one. Those counts come from their own
endpoint, deliberately — the indicator has to work while the journal panel is
closed, which is exactly when the entry list hasn't loaded.

Permissions match the service: anyone who can edit the garden can write, the
author can edit their own text, and the author or the garden owner can delete.
A viewer sees the entries and the count but no composer.

The empty state says what the journal is for rather than just "no entries",
since it starts empty for a whole season's worth of gardens and the reason to
start is the thing worth saying.

Closes #53

Co-Authored-By: Claude Opus 4.8 (1M context) <[email protected]>
Claude-Session: https://claude.ai/code/session_01H3zbym8Doka2d7D48maSgZ

internal/api/api.go

@@ -90,6 +90,7 @@ func New(cfg *config.Config, svc *service.Service) *gin.Engine {
 	// plop, so it inherits the ordinary garden-role check.
 	gardens.GET("/:id/journal", h.listJournal)
 	gardens.POST("/:id/journal", h.createJournalEntry)
+	gardens.GET("/:id/journal/counts", h.getJournalCounts)
 
 	// Sharing (owner-managed; a recipient may remove their own share).
 	gardens.GET("/:id/shares", h.listShares)