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]>

shared/time.js

@@ -1,11 +1,16 @@
 // Browser-safe. No node:* imports, no DOM. Imported by both server and browser.
 
 const DASHES = /[‒–—−-]/; // -, –, —, minus sign
+// Matches only the non-ASCII members of DASHES — used to fold a leading minus/en/em dash down to
+// an ASCII hyphen before sign detection, so a string like "−0:30" (U+2212, the character every
+// signed number in this app's own reference data — SYMPTOM_FIXES, cultivar profiles — is written
+// with) parses instead of silently returning null.
+const NON_ASCII_DASHES = /[‒–—−]/g;
 
 /** "8:45" -> 525, "-0:20" -> -20, "+0:15" -> 15, "0" -> 0, "90" -> 90 (bare seconds). null on junk. */
 export function parseDuration(str) {
   if (str === null || str === undefined) return null;
-  const s = String(str).trim();
+  const s = String(str).trim().replace(NON_ASCII_DASHES, "-");
   if (s === "") return null;
   const sign = s.startsWith("-") ? -1 : 1;
   const body = s.replace(/^[+-]/, "");