Own all form styling in components; remove form CSS from input.css

Form controls were styled "at a distance": Django renders bare
<input>/<select>/<textarea>/<label>, so input.css reached in with ID-scoped
#add-form descendant rules plus a global form *:disabled rule and .errorlist.
The #add-form ID specificity forced state rules to climb, needed
:not([data-search-select-search]) carve-outs, and broke on markup changes — it
surfaced as the add_purchase Name/related_game fields not reading as disabled.

Components now own all form styling via utilities on the elements themselves:

- PrimitiveWidgetsMixin stamps INPUT/SELECT/TEXTAREA_CLASS (incl. disabled:
  variants) onto native widgets by type, skipping SearchSelect (self-styled)
  and checkboxes.
- New FormFields(form, *, extras=...) renders label + control + errors + row
  layout with their own classes (replaces form.as_div()); the <form> owns its
  flex layout. extras appends a node into a named field's row (session
  timestamp buttons).
- AddForm/purchase/session render via FormFields; login too — a new
  LoginForm(PrimitiveWidgetsMixin, AuthenticationForm) styles its inputs and
  auth.py renders it via FormFields + a StyledButton (was as_table).
- input.css loses the entire #add-form block, the global :disabled rule, and
  .errorlist. State (disabled:) now lives on the element — no specificity wars,
  no carve-outs, robust to markup edits.

Tests: error rendering uses the component class (not .errorlist); add-form
labels/inputs carry their own classes; e2e login fixtures click the Login
button by text (submit is now a <button>); Name disabled cursor asserted.
CLAUDE.md documents the no-styling-at-a-distance + FormFields conventions.

513 passed; lint/format/ts-check clean.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

CLAUDE.md

@@ -189,6 +189,8 @@ Pytest settings are in `pyproject.toml` under `[tool.pytest.ini_options]` (`DJAN
 - **Signals handle side-effects** — do not manually recalculate `Game.playtime` or `Purchase.num_purchases`; the signals in `games/signals.py` do this on save/delete.
 - **Button colors**: `blue` (primary action), `red` (destructive), `gray` (secondary), `green` (positive). Icon buttons use `icon=True`.
 - **Inline Alpine.js** is used for client-side reactivity in domain components (`GameStatusSelector`, `SessionDeviceSelector`). The pattern is `x-data="{...}"` with `fetchWithHtmxTriggers()` for PATCH API calls.
+- **No styling-at-a-distance; elements carry their own classes**: `input.css` is document bootstrapping only (Tailwind import, theme, fonts, resets) — it contains **no form/component styling and no selectors that reach across the DOM** (`#id descendant`, `form input:disabled`, etc.) to style something a component owns. An element's appearance, **including state** (`disabled:`, `has-[:disabled]:`, `focus:`), comes from utility classes on that element, emitted by its component. This keeps state composable (no specificity wars) and robust to markup edits.
+- **Forms render via `FormFields`/`AddForm`, never `form.as_div()`**: `FormFields(form, *, extras=...)` (in `primitives.py`) renders label + control + errors + row layout with their own classes; native controls get their classes from `PrimitiveWidgetsMixin` (`games/forms.py`, which stamps `INPUT/SELECT/TEXTAREA_CLASS` incl. `disabled:` variants by widget type, skipping SearchSelect + checkbox). Every form is on this path, including login (`LoginForm(PrimitiveWidgetsMixin, AuthenticationForm)`). `extras` appends a node into a named field's row (e.g. the session timestamp buttons).
 - **Disabling composite widgets**: a composite widget (e.g. `SearchSelect`) carries its `id` on a wrapper `<div>`, which has no `disabled` state — setting `.disabled` on it is a no-op. Disable the inner control (for `SearchSelect`, the `[data-search-select-search]` input); the **component owns its disabled *look*** via `has-[:disabled]:` utilities on its container class, so callers toggle only the control's `disabled`, never styles.
 - **Platform icons** are SVG snippets in `games/templates/icons/<slug>.html`. Add new ones there and reference them by slug in `Platform.icon`.
 - **Name compound types explicitly** — if a `tuple`, `dict`, or other compound value is passed between functions or appears in multiple signatures, give it a named type (`TypedDict`, `NamedTuple`, or a `type` alias) rather than repeating the structural annotation. This applies even to small types used in only a few places; the name carries intent that the structure cannot. Examples: `LabeledOption = tuple[str, str]` instead of repeating `tuple[str, str]` for (value, label) pairs; `RangeValues(min, max)` instead of `tuple[str, str]` for range bounds.