i18n(ru): pluralize shared reading range captions

[kavemang]

What this PR does

The shared Russian reading-range captions currently use измерений for every count. Add one/few/many/other forms to %lld readings · %@ and %lld readings · sparse, widened to %@, used in Metric Explorer, Trends, Apple Health and Xiaomi detail views. Preserve existing many forms, indexed count/range arguments and all other catalog content. English singular branches remain unchanged; Russian one is still needed for 21, 31, etc.

Draft for native Russian review required by #573 and manual reading-caption displays/VoiceOver at 0/1/2/5/11/21/22/25, including filtered and widened ranges. Prior #2665 changed different Lab Book keys; this batch addresses only the shared range captions. No counts, filtering, range resolution, calculations or stored values change. Android uses independent locale resources.

Type of change

• Bug fix

How it was tested

• Focused JSON comparison: exactly two ru entries changed, four categories each, count/range argument sequences preserved; all other catalog content unchanged.
• Diff-scoped i18n audit, global doc-comment hygiene and whitespace checks passed. Local full Tools discovery: 338 tests passed. Upstream Tools: 234 capture, 50 parity acceptance, 2 R-R contract and 153 core Tools tests passed.
• Exact head e97f792d92fdee9d14455f8b25d1c918089a2216: all six expected checks passed. Apple SDK CI built universal macOS and iOS Simulator apps, including changed String Catalog compilation. Actual StrandTests: 2,267 tests, two skipped, zero failures. No warning attributed to the changed catalog found.
• Android CI built the APK; its unit-test task was FROM-CACHE, so no fresh Android execution is claimed. Android source unchanged.
• Linux cannot compile Apple SDK targets. No native grammar approval, manual UI/VoiceOver interaction or hardware validation claimed.

Checklist

• Follows docs/CONTRIBUTING.md; no generated output or secrets
• Layout and design tokens unchanged
• No BLE commands or hardcoded frames
• Swift packages/Android source unchanged; counts/range/filtering/stored data unchanged

Related issues

Refs #573