Quantum 0.21.0

Added

projects/helpdesk: tickets with an attachment and e-mail to the support team and the requester — in the browser and in the console.
q:file action="send" (FILE-2): a page answers with an uploaded file as a download, and decides who may have it. Uploads are never static files.
<ui:input rows="6">, a multi-line field (UI-14). A form whose action takes a file posts multipart and draws a file input with the param's accept.
mail: in quantum.config.yaml (MAIL-1); host: log writes messages to the log in development. q:mail name= and onerror="continue" (MAIL-2).
quantum check also checks the SQL in q:agent tools.
"Why Quantum" page (A6), with its example tested; the docs home no longer promises mobile apps or "40+ components".

q:mail sends through mail: in the config, and is an error without it. It read SMTP_* variables and, unless EMAIL_MOCK=false was set, printed "[MOCK] Email sent" and reported success — no application ever sent mail by default. Use ${SMTP_HOST} etc. in the config (CFG-1).
A message the server refuses stops the page or action (MAIL-2); it used to be an unhandled error too, but some recipients refused was reported as sent.
The result of q:mail is <name>_result (mail_result by default), not _mail_result.
q:param maxSize= is a parse error (the attribute is maxsize), and so is a maxsize that is not a size. q:file action= other than upload, delete or send is a parse error.
The upload result no longer has url: it pointed to /uploads/..., which was never served.

The repository is in English (EN): SPEC.md (rule IDs unchanged), the tests, the framework code, its messages and comments. Log and error texts that were Portuguese now read in English.
Support tiers (SUPPORT_TIERS.md, rewritten for 1.0): the tiers are Core, AI, Experimental and Laboratory. q:file, q:mail and q:transaction move to Core (SPEC rules, tests and an app in CI); q:team moves to Experimental (no rule, no proving app) and now warns once when used. The pytest markers are laboratory and isolated (were laboratorio and isolado).
The console's screen widget is #page (was #tela).
The wheel no longer ships the old FastAPI admin (quantum_admin/backend, ~2.6 MB with its 600 KB main.py). The library the .q admin uses moved to quantum_admin.core; quantum admin is unchanged. The backend stays in the repository (A4.2).
quantum/runtime/web_server.py (2150 lines) is split by concern: web_config (reading the config), web_html (asset extraction, htmx, hot reload), web_errors (welcome and error pages), web_lifecycle (start, banner, PID, signals). QuantumWebServer, create_app, start_server, ConfigError and _validate_config are imported from where they were.

quantum/cli/commands (new, dev, build, serve, test, lint, docs): a click CLI that the quantum command never wired, listed in the CLI docs as "future commands". The migration runner it held is now quantum.cli.migrations (quantum migrate is unchanged).

q:transaction failed validation on every run (quantum run: "Invalid isolation level: "): the parser passed the datasource where the node expected the isolation level, and kept the level where nothing read it. An explicit datasource= never reached the executor. An unknown isolationLevel is now a parse error (DB-4).
quantum run refused <ui:alert variant="{...}"> (and a bound variant or position on ui:toast/ui:skeleton) as an invalid literal; the page resolves it when it renders (UI-1).
q:param maxsize was parsed and never checked: any size was accepted.
q:file action="upload" without destination failed with "empty file path"; it saves under paths.uploads.
<ui:form submit="..."> with fields of its own drew no button.
<ui:table source="{rows}"> without ui:column drew every row empty; it shows one column per field (UI-5).
Sending mail looked up the machine's full name on every message (socket.getfqdn): 12 s for the first message on a Windows machine.
The test suite's admin database was shared by every pytest-xdist worker, which failed now and then with "table ... already exists".