chore(quality): resolve SonarQube code smells across website

Clears the 124 CODE_SMELL findings from the SonarQube scan (server, client,
and bot). All changes are behaviour-preserving refactors — no route, protocol,
schema, or config changes — verified against the full server (381) and client
(43) test suites plus a clean client build.

By rule:
- S3776 (20, cognitive complexity): extract helpers/handlers so each function
  drops under the threshold — shard model upsert builders, page/wiki update,
  block validation, notification stream mapping (dispatch table), SSO mobile
  login, shard ingest deps, uo-link socket backfill/connect, the bot slash-
  command dispatchers + discord manager, and the Shard/UserDetail/HeroEditor/
  CharacterStats React components.
- S4624 (34, nested template literals): pull inner templates into locals /
  a withQs() helper; rewrite shardEvents.describe() as a formatter table.
- S3358 (35, nested ternaries): lift to if/else vars, lookup maps, small
  components, or guarded JSX expressions.
- S6479 (12, array-index React keys): key by stable content instead of index
  (two in-editor lists left as-is; index matches their by-index edit model).
- S6353 (6): [0-9]/[^0-9] -> \d/\D.  S125 (5): reword state-shape comments that
  parsed as code.  S3800/S3782 (botScore): JSDoc-type PATH_WEIGHTS tuples.
- S6481 (2): memoize Auth/Site context values (and SiteContext brand).
- S4144: dedupe HeroEditor upload handler into useImageUpload().
- S1126 (2), S6035, S5869 (redundant A-Z under /i), S5843 (town-name regex ->
  prefix list): assorted one-liners.

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

client/src/contexts/AuthContext.jsx

@@ -1,4 +1,4 @@
-import { createContext, useContext, useEffect, useState, useCallback } from 'react'
+import { createContext, useContext, useEffect, useState, useCallback, useMemo } from 'react'
 import { api } from '../api/client.js'
 
 const AuthContext = createContext(null)
@@ -61,8 +61,15 @@ export function AuthProvider({ children }) {
     }
   }, [])
 
+  // Memoized so consumers don't re-render on every provider render (the callbacks
+  // are already stable via useCallback).
+  const value = useMemo(
+    () => ({ user, loading, login, register, loginTotp, ssoLoginTotp, logout, refresh }),
+    [user, loading, login, register, loginTotp, ssoLoginTotp, logout, refresh],
+  )
+
   return (
-    <AuthContext.Provider value={{ user, loading, login, register, loginTotp, ssoLoginTotp, logout, refresh }}>
+    <AuthContext.Provider value={value}>
       {children}
     </AuthContext.Provider>
   )