feat(web): Persona Generation page under AUTOMATION

New dashboard surface for editing the global emailgen persona pool —
the JSON file fleet (MACVLAN/IPVLAN) and SWARM-shard mail deckies pull
from.  MazeNET topology personas are out of scope here; they're
configured per-topology in the topology editor.

Backend:
* GET/PUT /api/v1/emailgen/personas — admin-write, viewer-read.  PUT
  validates with the same Pydantic schema the worker uses
  (parse_personas), drops invalid entries with a warning, returns 400
  only when the entire payload fails.  Path is operator-discoverable
  on every response so a CLI-driven backup workflow stays visible.

Frontend:
* PersonaGeneration.tsx + .css — table + add/edit modal with the full
  EmailPersona schema (name, email, role, tone, mannerisms list,
  language, signature, active hours, reply latency, uses_llms_heavily).
  Local edits are batched; explicit "SAVE CHANGES" writes back, with a
  dirty-indicator pill and a "DISCARD" reset.  Email uniqueness is
  enforced client-side so the scheduler never picks the same persona
  as both sender + recipient.
* Sidebar AUTOMATION group gains a "Persona Generation" entry next to
  Orchestrator; route registered at /persona-generation.

The worker reads the same on-disk file the API writes — see
decnet.orchestrator.emailgen.global_pool.  The API resets the
in-process cache on every read/write so the worker picks up dashboard
edits within its next tick rather than waiting on mtime.

decnet_web/src/App.tsx

@@ -24,6 +24,7 @@ const IdentityDetail = lazy(() => import('./components/IdentityDetail'));
 const Campaigns     = lazy(() => import('./components/Campaigns'));
 const CampaignDetail = lazy(() => import('./components/CampaignDetail'));
 const Orchestrator   = lazy(() => import('./components/Orchestrator'));
+const PersonaGeneration = lazy(() => import('./components/PersonaGeneration'));
 const Config         = lazy(() => import('./components/Config'));
 const Bounty         = lazy(() => import('./components/Bounty'));
 const Credentials    = lazy(() => import('./components/Credentials'));
@@ -123,6 +124,7 @@ const AuthedShell: React.FC<AuthedShellProps> = ({ onLogout, onSearch, searchQue
             <Route path="/campaigns" element={<Campaigns />} />
             <Route path="/campaigns/:id" element={<CampaignDetail />} />
             <Route path="/orchestrator" element={<Orchestrator />} />
+            <Route path="/persona-generation" element={<PersonaGeneration />} />
             <Route path="/config" element={<Config />} />
             <Route path="/swarm-updates" element={<RemoteUpdates />} />
             <Route path="/swarm/hosts" element={<SwarmHosts />} />