feat: cleaner TopBar + live scan progress wired end-to-end

Two related polish items.

1. Drop dead TopBar buttons
   - Removed the hamburger menu (Tab already toggles the sidebar),
     the grid/list view-mode toggle (only Grid was ever
     implemented), and the FolderOpen / Upload / Settings action
     icons (no features behind them).
   - TopBar is now: logo + active heap pill | search | filter
     toggle. Removed the now-unused Grid/List/Menu/FolderOpen/
     Upload/Settings icon imports and the dead viewMode local
     state.

2. Wire live scan progress
   - The frontend ScanProgress widget was already polling
     /api/v1/library/scan/status, but the worker never wrote the
     Redis keys that endpoint reads — it only updated celery's
     internal task state. So the progress UI was permanently idle.
   - Worker now writes scan:active / scan:current_folder /
     scan:processed_files / scan:total_files / scan:errors at
     every meaningful step. _get_redis() returns None on failure
     so a Redis outage degrades gracefully (scan still runs,
     progress just doesn't show).
   - Pre-walk computes total_files upfront — without it the
     progress bar jumped every time os.walk discovered a new
     subfolder because the running total was being updated as it
     went.
   - Errors are RPUSHed to a capped list (MAX_ERROR_ENTRIES=50)
     so a noisy scan can't blow up Redis.
   - finally: clause guarantees scan:active flips to false even
     on a crash, so the UI never sticks at "scanning" forever.
   - scan_all_source_roots clears scan:errors and resets counters
     before queuing the per-root tasks, so each top-level scan
     starts with a clean slate.

   Two latent bugs caught and fixed in passing:
   - watch_folders was still reading settings.source_roots which
     no longer exists since we moved source roots to the DB. Now
     it loads them from the DB via a synchronous one-shot async
     wrapper at task startup.
   - _scan_all_source_roots_async was missing entirely after the
     last refactor — defined inline now, reads active source
     roots from the DB and dispatches scan_folder per row.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

frontend/src/components/layout/TopBar.tsx

@@ -1,13 +1,7 @@
 import { useState, useEffect, useRef } from 'react'
 import {
   Search,
-  Grid,
-  List,
   SlidersHorizontal,
-  FolderOpen,
-  Upload,
-  Settings,
-  Menu,
   X,
   ShoppingBasket,
 } from 'lucide-react'
@@ -49,8 +43,6 @@ export function TopBar() {
     }
   }, [searchQuery, storeQ, setStoreQ])
 
-  const [viewMode, setViewMode] = useState<'grid' | 'list'>('grid')
-
   // Currently active heap. Shown as a pill so the user always knows where
   // their next P-press will land.
   const { data: heapsList = [] } = useHeapsQuery()
@@ -58,17 +50,8 @@ export function TopBar() {
 
   return (
     <header className="flex h-12 items-center justify-between border-b border-border bg-surface px-4">
-      {/* Left Section - Menu and App Name */}
+      {/* Left — logo + active heap pill */}
       <div className="flex items-center gap-3">
-        <button
-          className="group relative rounded p-1 text-text-muted hover:bg-surface-2 hover:text-text"
-          title="Toggle sidebar (Tab)"
-        >
-          <Menu className="h-5 w-5" />
-          <kbd className="absolute -bottom-5 left-1/2 -translate-x-1/2 rounded bg-surface-offset px-1 py-0.5 text-[9px] font-medium text-text opacity-0 group-hover:opacity-100">
-            Tab
-          </kbd>
-        </button>
         <div className="flex items-center gap-2">
           <img src={muliLogo} alt="Mulita" className="h-7 w-7 object-contain" />
           <h1 className="text-lg font-semibold text-text">Mulita</h1>
@@ -83,8 +66,8 @@ export function TopBar() {
           </span>
         )}
       </div>
-      
-      {/* Center Section - Search */}
+
+      {/* Center — search */}
       <div className="flex max-w-xl flex-1 items-center px-8">
         <div className="relative w-full">
           <Search className="absolute left-3 top-1/2 h-4 w-4 -translate-y-1/2 text-text-muted" />
@@ -117,38 +100,9 @@ export function TopBar() {
           )}
         </div>
       </div>
-      
-      {/* Right Section - View Controls and Actions */}
+
+      {/* Right — filter toggle */}
       <div className="flex items-center gap-2">
-        {/* View Mode Toggle */}
-        <div className="flex rounded-md border border-border">
-          <button
-            className={clsx(
-              'rounded-l-md px-2 py-1',
-              viewMode === 'grid' 
-                ? 'bg-primary text-white' 
-                : 'bg-surface text-text-muted hover:bg-surface-2'
-            )}
-            onClick={() => setViewMode('grid')}
-            title="Grid view"
-          >
-            <Grid className="h-4 w-4" />
-          </button>
-          <button
-            className={clsx(
-              'rounded-r-md px-2 py-1',
-              viewMode === 'list' 
-                ? 'bg-primary text-white' 
-                : 'bg-surface text-text-muted hover:bg-surface-2'
-            )}
-            onClick={() => setViewMode('list')}
-            title="List view"
-          >
-            <List className="h-4 w-4" />
-          </button>
-        </div>
-        
-        {/* Filter Button */}
         <button
           onClick={toggleFilterBar}
           className={clsx(
@@ -164,31 +118,7 @@ export function TopBar() {
             \
           </kbd>
         </button>
-        
-        <div className="mx-1 h-6 w-px bg-border" />
-        
-        {/* Action Buttons */}
-        <button
-          className="rounded p-1.5 text-text-muted hover:bg-surface-2 hover:text-text"
-          title="Add folder"
-        >
-          <FolderOpen className="h-4 w-4" />
-        </button>
-        
-        <button
-          className="rounded p-1.5 text-text-muted hover:bg-surface-2 hover:text-text"
-          title="Import photos"
-        >
-          <Upload className="h-4 w-4" />
-        </button>
-        
-        <button
-          className="rounded p-1.5 text-text-muted hover:bg-surface-2 hover:text-text"
-          title="Settings"
-        >
-          <Settings className="h-4 w-4" />
-        </button>
       </div>
     </header>
   )
-}
+}