docs: update architecture docs and diagrams for recent changes

ARCHITECTURE.md:
- Directory structure: add middleware/requireAuth.js and favicon assets
- §4.1: remove CORS from middleware list
- §4.2: all proxy routes now auth-required via requireAuth; add
  middleware description
- §6: cookie payload corrected (no token); document secure+sameSite
- §7: add emby:users cache key (60s TTL)
- §8: Download Object table: userTag → allTags/matchedUserTag/tagBadges
- §9 POST /login: document cookie security attributes
- §10: add Tag Badge Rendering section; remove hardcoded line count

Diagrams:
- class-server.puml: add requireAuth middleware module; update
  dashboard.js methods (extractAllTags, extractUserTag w/ username,
  buildTagBadges, getEmbyUsers); add TagBadge value class; add auth
  relationships for all proxy routes
- class-data.puml: Download Object userTag → allTags/matchedUserTag/
  tagBadges; add TagBadge class; remove token from Session Cookie
- seq-auth.puml: cookie payload no longer contains token; add
  secure/sameSite note
- component.puml: remove CORS component; add requireAuth; consolidate
  Emby connection to show tag badge + user-summary usage
- activity-matching.puml: update to extractAllTags/extractUserTag
  (with username); showAll uses hasAnyTag; tagBadges built from
  embyUserMap; add Emby user fetch step; update legend
- seq-dashboard.puml: add emby:users cache lookup / Emby fetch for
  showAll; update matching groups to show tag classification; add
  tag badge rendering note on renderDownloads()

docs/diagrams/component.puml

@@ -16,10 +16,10 @@ package "Browser" as browser {
 package "Express Server" as server {
 
   package "Middleware" {
-    [CORS] as cors
     [cookie-parser] as cp
     [express.json] as ej
     [express.static] as es
+    [requireAuth.js] as requireauth
   }
 
   package "Routes" as routes {
@@ -41,7 +41,6 @@ package "Express Server" as server {
 
   [index.js\nEntry Point] as entry
 
-  entry --> cors
   entry --> cp
   entry --> ej
   entry --> es
@@ -51,6 +50,12 @@ package "Express Server" as server {
   entry --> sab_route
   entry --> sonarr_route
   entry --> radarr_route
+
+  emby_route --> requireauth
+  sab_route --> requireauth
+  sonarr_route --> requireauth
+  radarr_route --> requireauth
+  dashboard --> requireauth
   entry --> poller : startPoller()
 
   dashboard --> cache : read poll:* keys
@@ -76,7 +81,7 @@ cloud "External Services" as external {
 }
 
 auth --> emby : authenticate\nuser profile
-dashboard ..> emby : /user-summary\n(live fetch)
+dashboard --> emby : GET /Users\n(user-summary + tag badge classification)
 emby_route --> emby
 sab_route --> sab
 sonarr_route --> sonarr