Massive rework of platform layer user/organization

The goal of this rework is to make it so I can pass around platform.User
instead of a pair of models.Organization and models.User. This is useful
for reason I kind of forget now, but it started with working on
notifications and ballooned massively from there into refactoring a
number of things that were bugging me.

This also includes a tiny amount of work on server-side events (SSE).

 * background stuff lives inside the platform now, which I need for
   having it push updates through SSE
 * userfile now lives in the platform, under file, so other platform
   functions can safely use it
 * oauth is broken into pieces and inside platform because other stuff
   was calling it already, but badly.
 * notifications go into the platform as well

platform/publicreport/nuisance.go

@@ -96,3 +96,19 @@ func NuisanceReportForOrganization(ctx context.Context, org_id int32) ([]Nuisanc
 	}
 	return reports, nil
 }
+func NuisanceReportForOrganizationCount(ctx context.Context, org_id int32) (uint, error) {
+	type _Row struct {
+		Count uint `db:"count"`
+	}
+	row, err := bob.One(ctx, db.PGInstance.BobDB, psql.Select(
+		sm.Columns(
+			"COUNT(*) AS count",
+		),
+		sm.From("publicreport.nuisance"),
+		sm.Where(psql.Quote("publicreport", "nuisance", "organization_id").EQ(psql.Arg(org_id))),
+	), scan.StructMapper[_Row]())
+	if err != nil {
+		return 0, fmt.Errorf("query count: %w", err)
+	}
+	return row.Count, nil
+}