chore(release): v1.28.28 — OpenAI-compatible gateways work; a re-keyed night can no longer vanish

The Local provider speaks the standard JSON wire: response_format by default,
one self-healing fallback per endpoint when a server rejects it (dialect
cached per base URL) — LiteLLM, OpenRouter, vLLM, LM Studio and plain Ollama
all work from the same form, and the form + provider docs now say so. A
gateway that shims a Claude-family model behind a synthesized tool call is
parsed from the tool-call arguments instead of yielding silently empty
insights.

The insight token budget is configurable (INSIGHTS_MAX_TOKENS, default 2500,
clamped 500-8000) and unified across all six call sites; a reply cut off
mid-JSON returns a distinct truncation error instead of a generic parse
failure. A briefing withheld by the number-grounding check now says so on the
card instead of pretending nothing was generated. The provider test button
answers 4xx with a bad_request category instead of claiming the endpoint was
unreachable.

Sleep repair follow-up: measurements carries a second full unique index — the
natural key (type, measured_at, source, sleep_stage) — so a key-format
migration could tombstone the old rows while their re-keyed replacements
collided with that index and were silently dropped (live incident: a
full-history re-sync erased a user's sleep). Planned creates now run a
natural-key rescue probe: a match, live or tombstoned, is updated in place —
fresh value, the new externalId, deletedAt cleared. A rescue-probe failure
holds the watermark so nothing is lost past the overlap.

docs/api/openapi.yaml

@@ -1,7 +1,7 @@
 openapi: 3.1.0
 info:
   title: HealthLog API
-  version: 1.28.27
+  version: 1.28.28
   description: >-
     Self-hosted personal-health-tracking PWA — public API surface for the iOS native client and external ingest.