1.5.0

Fixed — every brand sent as whoever the process had sent as first

MailChannel and notifications:send-digests both ended in Mail::to(...)->send(...). That is
the process-wide default mailer with the process-wide mail.from, identically for every brand.
A host serving several brands out of one queue worker — or one digest run walking its brand list —
therefore delivered the second brand's mail under the first brand's name and address, and a relay
that verifies sending domains per account (Scaleway TEM, Postmark, SES) answers that by refusing
the message or rewriting the From to whichever identity the shared account owns. Either way the
recipient hears from the wrong company, and nothing turns red.

Who a notification goes out as is now resolved per message, from values, and never from config.
Contracts\SenderIdentityResolver answers "which mailer, which From, which locale for brand N";
Sending\BrandMailer is the single door both send paths leave through, and it puts the answer on
the message (Mailable::from(), Mail::mailer($name)).

Not on the config, deliberately: Laravel reads mail.from the first time a mailer name is resolved,
burns it into that mailer instance via alwaysFrom(), and caches the instance in the mail.manager
singleton. A scoped Config::set therefore escapes its own finally — whichever brand sends first
leaves its address standing for the rest of the process. That is the same bug one layer down, and
it is why nothing here writes to mail.*.

Fixed — the digest could burn a recipient's window without sending anything

DigestBuilder::markSent() stamps digested_at on every collected item before the mail leaves.
A brand that cannot produce a usable sender identity would have had each recipient's whole window
marked as delivered with nothing delivered, and the items would never have resurfaced. The check
now runs in front of the recipient loop: the brand is skipped, nothing is collected, nothing is
stamped, and everything stays pending until the settings are fixed.

Changed — a brand that declares a broken mail identity sends nothing

Read from brands.settings.mail:

key	meaning
from_address	required once mail is present at all
from_name	defaults to the brand name
mailer	a mailer from config/mail.php
locale	the language its mail is written in

A brand that declares mail without from_address, or names a mailer that config/mail.php
does not define, now sends nothing and says so at error level (throttled per brand, so a
fan-out cannot bury it). The alternative was delivering under the host-wide From, which on a
multi-brand host is somebody else's identity — quietly.

A single-brand install is unchanged, and that is covered by tests rather than intent. So is a
multi-brand install whose brands carry no settings.mail: no brand, or no mail settings, resolves
to the config identity and the send is byte for byte the one it always was. A host that keeps
sender identities somewhere else rebinds SenderIdentityResolver in its own provider instead of
patching this package.