feat(ssr): migrate location-select to a Selmer template (Phase 2 — Selmer validated)

First interactive Transaction Edit component rendered from a Selmer template instead of
Hiccup/com/select, proving the render-file path + the Hiccup<->Selmer interop bridge on
real, e2e-covered markup.

- resources/templates/components/location-select.html: plain-HTML <select> with a
  {% for %} over option maps + {% if opt.selected %}.
- location-select*: build options/selected/classes in Clojure (reusing
  inputs/default-input-classes so styling can't drift), render via
  sel/render->hiccup, and embed the fragment back into the still-Hiccup account row.
- skill: finalize selmer-conventions.md from this validated example (was a stub); add the
  cookbook entry; scorecard marks the first Selmer component.

Verified on a fresh server: full suite 38 pass / 1 unrelated fail, swap 6/6,
transaction-edit 8/8 -- the Shared Location test selects through the Selmer <select>,
saves, and spreads Shared -> DT. Verified by string-match + e2e (not byte-parity:
hh/add-class is set-based so class order differs, CSS is order-independent).

Scope note: the modal's remaining attribute-heavy components delegate to the shared
com/typeahead / com/select / com/button-group-button; converting those is the
cross-cutting Phase 11 Selmer sweep, not a single-modal change (Open decision 2).

src/clj/auto_ap/ssr/transaction/edit.clj

@@ -21,11 +21,13 @@
    [auto-ap.ssr-routes :as ssr-routes]
    [auto-ap.ssr.common-handlers :refer [add-new-entity-handler]]
    [auto-ap.ssr.components :as com]
+   [auto-ap.ssr.components.inputs :as inputs]
    [auto-ap.ssr.grid-page-helper :as helper]
    [auto-ap.ssr.transaction.common :refer [grid-page]]
    [auto-ap.ssr.components.multi-modal :as mm]
    [auto-ap.ssr.form-cursor :as fc]
    [auto-ap.ssr.hx :as hx]
+   [auto-ap.ssr.selmer :as sel]
    [auto-ap.ssr.svg :as svg]
    [auto-ap.ssr.utils
     :refer [->db-id apply-middleware-to-all-handlers check-allowance
@@ -36,6 +38,7 @@
    [bidi.bidi :as bidi]
    [clj-time.coerce :as coerce]
    [clojure.edn :as edn]
+   [clojure.string :as str]
    [datomic.api :as dc]
    [hiccup.util :as hu]
    [iol-ion.query :refer [dollars=]]
@@ -153,20 +156,29 @@
       (:vendor/default-account clientized))))
 
 (defn location-select*
+  "The location <select> for an account row, rendered from a Selmer template
+   (templates/components/location-select.html) -- the first interactive modal component
+   migrated off Hiccup. Same options/selection/styling as the old com/select, emitted as
+   plain HTML and embedded back into the Hiccup row via the interop bridge."
   [{:keys [name account-location client-locations value]}]
-  (let [options (into (cond account-location
-                            [[account-location account-location]]
+  (let [options (cond account-location
+                      [[account-location account-location]]
 
-                            (seq client-locations)
-                            (into [["Shared" "Shared"]]
-                                  (for [cl client-locations]
-                                    [cl cl]))
-                            :else
-                            [["Shared" "Shared"]]))]
-    (com/select {:options options
-                 :name name
-                 :value (or value (ffirst options))
-                 :class "w-full"})))
+                      (seq client-locations)
+                      (into [["Shared" "Shared"]]
+                            (for [cl client-locations]
+                              [cl cl]))
+
+                      :else
+                      [["Shared" "Shared"]])
+        selected (or value (ffirst options))
+        classes (str/join " " (conj (vec inputs/default-input-classes) "w-full"))]
+    (sel/render->hiccup
+     "templates/components/location-select.html"
+     {:name name
+      :classes classes
+      :options (for [[v label] options]
+                 {:value v :label label :selected (= v selected)})})))
 
 (defn account-typeahead*
   [{:keys [name value client-id x-model]}]