refactor(frontend): the last pay-down, part 1 — three dead views deleted, editor rules shared, .page-container + .fs-input canon, rules-shared.css; a one-declaration CSS body is not a shape (#2903, milestone 299 step 5)

The derive queue said the biggest duplicate families were whole views:
TaskViewerView, UserManagementView and LogsView were imported nowhere — left
behind when tasks moved to the editor and users/logs became SettingsView
tabs. Deleted (rule 22). Note/TaskEditorView carried six identical scoped
rules -> editor-shared.css (the .tag-suggest-row gap the scoped copies
actually rendered wins). Three views wrapped the page under three names ->
.page-container in components.css. Three scoped input recipes -> the design
system fs-input recipe (snippet #2336), verbatim, in components.css; width/
box-sizing stay with the caller. The three rules panes share .pane and the
pane heading via rules-shared.css (the auth-shared pattern, #2852).

Ledger: a single-declaration CSS rule keeps its selector in its fingerprint,
so `color: var(--fs-text-tertiary)` under five different names is no longer
a five-file "identical body" family — the first pay-down found that most of
the 148 dup families were exactly this, and nobody would consolidate them.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

frontend/src/views/ProjectListView.vue

@@ -171,7 +171,7 @@ function overallPct(project: Project): { total: number; pct: number } {
 </script>
 
 <template>
-  <main class="projects-list">
+  <main class="page-container">
     <div class="page-header">
       <h1>Projects</h1>
       <button class="btn-primary" @click="openNewProjectModal">+ New Project</button>
@@ -336,13 +336,6 @@ function overallPct(project: Project): { total: number; pct: number } {
 </template>
 
 <style scoped>
-.projects-list {
-  max-width: var(--fs-layout-page-max);
-  margin: 2rem auto;
-  padding: 0 var(--fs-layout-page-pad);
-  overflow-x: clip;
-}
-
 .page-header {
   display: flex;
   justify-content: space-between;