feat(emailgen): Ollama-driven fake email worker for IMAP/POP3 deckies

Second orchestrator worker (decnet emailgen) that drips persona-driven,
threaded, multi-language fake emails into running mail deckies.  Personas
live on Topology.email_personas; topology-wide language_default falls
through to any persona that doesn't pin its own.  Em-dashes are
suppressed at the prompt layer by default and only lifted for personas
explicitly marked uses_llms_heavily — em-dashes are an LLM tell and a
flat corpus of em-dashed mail is a giveaway.

EML delivery writes into /var/spool/decnet-emails/<thread>/<msg>.eml on
the mail decky via docker exec; wiring the IMAP/POP3 templates to read
from that spool (replacing the hardcoded _BAIT_EMAILS) is the next step.

decnet/web/db/models/orchestrator.py

@@ -60,3 +60,52 @@ class OrchestratorEventsResponse(BaseModel):
     limit: int
     offset: int
     data: List[dict[str, Any]]
+
+
+class OrchestratorEmail(SQLModel, table=True):
+    """One fake email generated by the ``decnet emailgen`` worker.
+
+    Sibling table to :class:`OrchestratorEvent` — kept disjoint because
+    email rows carry domain-specific fields (subject, message_id,
+    in_reply_to, language) that have no analogue in the SSH/file events
+    and would otherwise bloat ``OrchestratorEvent.payload``.
+
+    The mail decky's UUID lives in ``mail_decky_uuid`` (the host serving
+    the IMAP/POP3 mailbox).  ``thread_id`` is a worker-side UUID used to
+    chain replies; ``in_reply_to`` is the parent email's RFC 2822
+    Message-ID header value (or ``None`` for thread roots).
+
+    ``payload`` follows the same loose-JSON convention as
+    :class:`OrchestratorEvent`: ``bytes``, ``generation_ms``, ``model``,
+    ``mannerisms_used``, etc.  The worker can extend it without a
+    migration.
+    """
+    __tablename__ = "orchestrator_emails"
+    __table_args__ = (
+        Index("ix_orchestrator_emails_mail_ts", "mail_decky_uuid", "ts"),
+        Index("ix_orchestrator_emails_thread", "thread_id"),
+    )
+    uuid: str = Field(default_factory=lambda: str(uuid4()), primary_key=True)
+    ts: datetime = Field(
+        default_factory=lambda: datetime.now(timezone.utc), index=True
+    )
+    mail_decky_uuid: str = Field(index=True)
+    thread_id: str = Field(index=True)
+    message_id: str = Field(max_length=255)
+    in_reply_to: Optional[str] = Field(default=None, max_length=255)
+    sender_email: str = Field(max_length=255, index=True)
+    recipient_email: str = Field(max_length=255, index=True)
+    subject: str = Field(max_length=512)
+    language: str = Field(max_length=8, default="en")
+    eml_path: str = Field(max_length=1024)
+    success: bool = Field(default=False, index=True)
+    payload: str = Field(
+        sa_column=Column("payload", Text, nullable=False, default="{}")
+    )
+
+
+class OrchestratorEmailsResponse(BaseModel):
+    total: int
+    limit: int
+    offset: int
+    data: List[dict[str, Any]]