Add per-user learned machine profile; fix methodology honesty issues

Replaces the flat additive batch-size correction with a per-user
multiplicative pace factor learned from each account's own logged
roasts (shared/learn.js, GET /api/machine-profile), plus a lot-scoped
"last refine" auto-suggestion. Also fixes the reference data being
framed as "your own roasts" on a now-multi-user product, and
reclassifies the drying/Maillard sanity checks as informational since
they're algebraically derived from the DTR check rather than
independent (yellow = 0.56 x first crack, not entered separately).

Bug fixes found by an adversarial Opus review of the first pass:
- Unicode minus sign (U+2212) broke duration parsing against the
  app's own generated refine-suggestion text
- Printed sanity-checks table still showed a bare pass/fail glyph for
  the now-informational drying/Maillard rows
- Printed time-ledger box didn't show the pace multiplication step,
  so it stopped reconciling by hand once pace != 1
- Field 6.4 (manual batch correction) was double-counted: excluded
  from the learned-pace fit but added back after the multiplication
- Learned pace had no outlier rejection or hard clamp
- computeLedger had no test coverage
- Batch-size help copy overstated what the pace factor models (it's
  a single blanket ratio, not conditioned on batch weight)

A follow-up Opus pass also caught the per-user profile cache
surviving logout/account-switch in a shared browser; fixed by
sweeping it alongside the existing plan-draft cleanup.

Co-Authored-By: Claude Sonnet 5 <[email protected]>

public/app.css

@@ -1625,6 +1625,28 @@ body.show-fids .field[data-fid]::after {
 .check-tile.fail .check-why {
 	display: block;
 }
+.check-tile.informational .check-why {
+	display: block;
+}
+.check-tile.informational .check-band {
+	font-style: italic;
+}
+.refine-suggestion {
+	margin-top: 6px;
+	padding: 8px 10px;
+	border-radius: var(--radius-sm);
+	border: 1px solid var(--ember-soft);
+	background: var(--ember-soft);
+	display: flex;
+	flex-direction: column;
+	align-items: flex-start;
+	gap: 6px;
+}
+.refine-suggestion span {
+	font-size: 11.5px;
+	color: var(--ink-2);
+	line-height: 1.4;
+}
 .dock-note {
 	font-size: 10.5px;
 	color: var(--ink-3);
@@ -2796,6 +2818,10 @@ body.show-fids .field[data-fid]::after {
 	td.passcell.fail::before {
 		content: "✗ ";
 	}
+	td.passcell.informational::before {
+		content: "— ";
+		color: var(--mid);
+	}
 }
 
 /* ─── Legacy .opt styling reused by the (hidden-on-screen) print worksheet's own radios ── */