Fix final-review findings: unit-label baseline, sqrt minor-tick math, dead code, edge cases

- Unit label was vertical-centered on a box derived from a baseline
  coordinate, shifting it 3.34mm too low and making the generated
  deliverables inconsistent with E440-Scale_template.svg. UNIT_Y is now
  used directly as the baseline; regenerated E440-Scale_paths.svg and
  E440-Scale_text.svg accordingly.
- sqrt scale's minor-tick angle formula double-applied the square-root
  mapping, badly misplacing minor ticks. Removed the special case so sqrt
  falls through to the already-correct generic value-interpolation branch.
  Corrected README's sqrt row (crowds toward the high end, not low).
- Removed dead code: unused _has_markup(), identity-transform wrapper and
  _UNIT_SCALE_X in _markup_unit_svg, unreachable max_val<=0 check,
  redundant math.isinf() in the minor-tick condition.
- Linear scale with min==max now raises ValueError like the other three
  mappings, instead of silently producing a degenerate dial.
- Form numeric parsing moved inside the try/except so bad input returns
  400 instead of crashing with 500.
- left_label/right_label now split on splitlines() to handle CRLF from
  browser textareas correctly.
- Formatting consistency: PIVOT_CIRCLE_R/R0 use :.5f like other constants;
  font_face indentation matches its sibling elements.
- LICENSE and CLAUDE.md: last M1730-Scale references and a doc inaccuracy
  about which labels are live text vs. outlined paths.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

CLAUDE.md

@@ -14,7 +14,7 @@ The three SVG files represent layers of the same design, intended to be combined
 
 - **`E440-Scale_template.svg`** — Inkscape working template. Contains the case body path (with mounting ears and rim cutout), the pivot guide circle, tick marks, numeric labels `0`–`50`, the `uA` unit label, and `Text`/`Left` and `Text`/`Right` corner label placeholders.
 - **`E440-Scale_paths.svg`** — Paths-only version: all tick marks and text as `<path>`/`<line>` elements, no live text. Used for cutting/printing workflows where fonts must not be embedded as live text.
-- **`E440-Scale_text.svg`** — Text-overlay version: tick mark lines plus live `<text>` elements for numeric/unit/corner labels, font embedded as base64.
+- **`E440-Scale_text.svg`** — Text-overlay version: tick mark lines plus live `<text>` elements for numeric/corner labels (the unit label is always emitted as outline paths since it supports markup), font embedded as base64.
 
 ## Key Design Parameters