Capture screens: move Water / expense-add / Sales add-line forms into dialogs? #133

Split out of #131, which migrated the CRUD and per-row surfaces to modal dialogs (PR #132).

Some forms were deliberately left inline because they are the whole point of the screen they sit on, not an interruption to a list:

• Water — the reading form is the screen
• Expenses — recording an expense (the category and correction forms did move in Inline add/edit forms → modal dialogs (less-intrusive capture) #131)
• Sales — adding a line to a draft order (the order itself and payment did move in Inline add/edit forms → modal dialogs (less-intrusive capture) #131)

Plus one surface #131 simply missed, tracked here rather than in a new issue:

• Users — the flock-assignment control in an expanded worker row (UsersPage.tsx:227) is still an inline-form div. That is a per-row action, so it was in Inline add/edit forms → modal dialogs (less-intrusive capture) #131's stated scope.

Daily entry is settled — #134 decides it

Daily entry was originally listed here. It no longer is: #134 answers it by construction, and the answer is inline.

• Daily entry UX: numbered sections, sticky summary footer, draft-edit badge (wizard rejected) #134 rejects a wizard because Daily entry is the highest-traffic, habitual screen and every extra step is a per-day cost. A dialog is an extra step, on every visit — the same argument reaches the same verdict.
• Its design specifies a sticky footer carrying the sellable-math line and both save actions. Inside a dialog that competes with .dialog-foot, and on mobile with the bottom sheet, which already owns the bottom edge.
• Its section ① contains the "+ new flock" dialog, which would nest a dialog inside a dialog.

No separate decision needed. #134's "Relationship to #133" note claiming independence is superseded.

The question, for what remains

Consistency says every capture form should behave the same way. Daily use says the opposite: a screen whose form is the screen becomes a table plus one button.

Water is the strongest remaining case for staying inline — same shape as Daily entry, lower traffic. Expenses-add is the weakest: it already has two sibling dialogs on the same screen. Sales add-line sits between — the draft panel is a work surface, but adding lines is repetitive and a dialog per line would grate. Users flock-assignment is not really a judgement call; it is a per-row action that should match its neighbours.

If we do it

• same Dialog component, same contract (Inline add/edit forms → modal dialogs (less-intrusive capture) #131) — no new UI work
• affected Vitest suites need the same open-the-dialog-first treatment
• decide per screen rather than as a batch

Decide first, then implement

Not obviously worth doing beyond the Users fix. Parking it as an explicit decision rather than an oversight — if the capture forms stay inline, the Help page already documents why ("Adding & correcting"), and this can close as won't-do once Users is handled.

Part of epic #14.