feat(emailgen): global persona pool + Date-stamped EML mtimes

Two changes that unwind earlier MazeNET-only assumptions and fix a
realism tell:

1. Persona resolution is now per-decky-source, not topology-only.  The
   scheduler walks the union view (list_running_deckies, including
   fleet MACVLAN/IPVLAN + SWARM shards) and picks the right persona
   list for each source:
     * topology decky -> Topology.email_personas (per-topology richness
       preserved)
     * fleet / shard  -> a single host-wide pool loaded from disk
       (DECNET_EMAILGEN_PERSONAS, /etc/decnet/email_personas.json, or
       ~/.decnet/email_personas.json)
   Operators install the global pool via 'decnet emailgen
   import-personas <file>' which validates with the same Pydantic
   schema the worker uses.

2. The driver now runs 'touch -d <Date>' inside the docker exec right
   after the EML write so file mtime matches the email's RFC 2822
   Date: header.  Without this an attacker 'ls -lt'ing the spool sees
   every email clustered inside the worker's tick window — the
   cluster itself was a stylometric tell.

CLI now exposes 'decnet emailgen' as a sub-app with 'run' (default,
backwards-compatible with bare 'decnet emailgen') and 'import-personas'.
list_running_deckies carries topology_id through so consumers can resolve
the parent topology without a second round-trip.

decnet/web/db/sqlmodel_repo.py

@@ -2119,13 +2119,17 @@ class SQLModelRepository(BaseRepository):
 
     async def list_running_deckies(self) -> list[dict[str, Any]]:
         out: list[dict[str, Any]] = []
-        # MazeNET — already shaped {uuid, name, ip, services}
+        # MazeNET — already shaped {uuid, name, ip, services}.  We carry
+        # topology_id through so consumers (emailgen scheduler) can walk
+        # back to the parent topology row without a second round-trip;
+        # fleet/shard rows never have one, hence Optional.
         for d in await self.list_running_topology_deckies():
             out.append({
                 "uuid": d.get("uuid"),
                 "name": d.get("name"),
                 "ip": d.get("ip"),
                 "services": d.get("services") or [],
+                "topology_id": d.get("topology_id"),
                 "source": "topology",
             })
         # Fleet — column is `decky_ip`, PK is composite (host_uuid, name)