fix(server): repair the initial-connect outbox envelope and unblock dispatch

ApplyInitialConnectPlan wrote a payload of {match_id,state,action},
omitting event, revision, resource_id, occurred_at and player_ids --
every field deliverStateOutboxEvent requires. Delivery rejected the row,
dispatch returned on the first error so it was never acknowledged, and
because reads are ordered oldest-first it was retried ahead of every
later state_changed event on every 100ms poll. One initial-connect
transition therefore blocked lifecycle delivery for all matches, not
just its own.

Two independent fixes, since either alone leaves the system fragile:

Build envelopes through one validating helper (MarshalOutboxEnvelope)
and convert all five writers to it. A writer that omits a required
field now fails its own transaction instead of committing a row that
can only ever poison the queue. The helper takes revision as int64 so
the -1 "nothing matched" sentinel some CTEs return surfaces as an error
rather than wrapping to a huge uint64.

Make dispatch resilient regardless: a delivery failure is now counted
against that row and the batch continues, with the row dead-lettered
after MaxOutboxDeliveryAttempts so a poison event degrades to one lost
notification instead of a stalled queue. Ordering within an aggregate
is still honoured -- later events of a failed match are deferred, so no
client observes that match's newer state before its older state. An ack
failure still stops the batch, being a database rather than a payload
problem.

Initial-connect events now address every participant, not just the
connected ones: a no-show needs to learn their ticket was failed and a
penalty applied.

server/store/proposal_sql.go

@@ -3,7 +3,6 @@ package store
 import (
 	"context"
 	"database/sql"
-	"encoding/json"
 	"fmt"
 	"time"
 
@@ -54,9 +53,9 @@ func CreateProposal(ctx context.Context, db *sql.DB, proposal domain.Proposal, t
 			}
 			players = append(players, participant.PlayerID)
 		}
-		payload, err := json.Marshal(map[string]any{
-			"event": "proposal_changed", "revision": uint64(0), "resource_id": proposal.ProposalID,
-			"occurred_at": now, "state": string(proposal.State), "player_ids": players,
+		payload, err := MarshalOutboxEnvelope(OutboxEnvelope{
+			Event: "proposal_changed", ResourceID: proposal.ProposalID, Revision: 0,
+			OccurredAt: now, State: string(proposal.State), PlayerIDs: players,
 		})
 		if err != nil {
 			return err