docs: align README environment variables with supported configuration

[2160039878-cyber]

Description

The README environment table omits custom, LLM_API_URL, and STORAGE_SQLITE_PATH. Add the missing configuration so readers can configure a self-hosted OpenAI-compatible endpoint and choose a SQLite storage file.

Type of Change

• Documentation update

Related Issue

Closes #666

Changes Made

The provider list and SQLite path wording follow DOCKERHUB.md. DOCKERHUB groups the four LLM variables into one row; the README retains its existing per-variable rows and explains URL selection using the actual resolver and .env.example: custom requires an explicit URL, while Ollama defaults to http://localhost:11434/v1. bun run readme:check passed. Documentation only; no executable lines change and the issue explicitly requires no new test.

Testing

• Local: bun run readme:check passed.
• Linux CI on the exact PR commit 496187b: 14,713 tests passed, all 391 isolated core files and 34 component groups passed; 46324/46324 lines covered (100%). Ran the unfiltered bun run test:coverage and bun run coverage:check scripts.
• The same run passed formatting, lint, typecheck, knip, README/chart/channel/security guards, application and library builds, Helm lint, and Node 24/26 engine smoke tests.
• Playwright: 65 passed / 1 flaky (passed on retry) / 6 skipped under the existing configuration, plus 1 subpath, 1 PostgreSQL functional smoke, 3 tarball, and 3 npx tests passed.
• Secret Scan passed after fetching all fork branch history, including this commit; no leaks found.

I did not complete bun run test / full coverage, the Helm checks, and E2E locally on Windows: the existing SQLite cleanup hits EBUSY, and Docker Desktop is unavailable. The unchanged upstream workflow ran the complete coverage/test layers and the other checks above on Linux instead. SonarCloud is the sole failed job in that fork run: access to the upstream project returns 401 / Not authorized or project not found. Upstream CI already skips SonarCloud for external fork PRs; no workflow or coverage gate was changed.

Test Environment

LibreDB Studio 0.15.0; Windows local / Ubuntu CI; Bun 1.4.2; Node 24 (plus Node 26 smoke); Chromium and WebKit; PostgreSQL functional smoke.

Checklist

• Claimed the linked issue before editing; branch starts from main.
• Reviewed the diff and followed the existing style.
• Documentation only: the issue explicitly requires no new test.
• All executable test/build jobs pass on the exact commit in Linux CI.

Additional Notes

AI-assisted implementation and validation using Codex, disclosed in the issue claim. Only documentation changes. No provider code changes, so the provider code/doc/test triad is not applicable. No dependent changes or screenshots are needed.

CI follow-up

The fork-run SonarCloud 401 is tracked in #732 and fixed by #733. The inherited condition admitted fork-owned pushes and fork-local PRs to the canonical SonarCloud project. The dedicated CI fix run now succeeds: all nine executable test/build jobs pass, and SonarCloud is scoped to the canonical repository. That run tests CI fix commit 80a318b; this PR's exact-head verification remains the original run linked above, whose nine executable jobs passed. Upstream Actions still await maintainer approval.

[cevheri]

Checked against #666. All four "Done when" items hold. The STORAGE_SQLITE_PATH row is byte-identical to DOCKERHUB.md:203, and the LLM_PROVIDER row keeps DOCKERHUB's AI: ... prefix and adds only the parenthetical the issue asked for. That was the point of the issue, so the two tables agree instead of offering a third phrasing.

LLM_API_URL had no single-variable counterpart to copy, since DOCKERHUB folds the four LLM variables into one row, so you wrote that description yourself. I checked both of its claims: validateConfig throws "Custom provider requires LLM_API_URL environment variable." when it is missing, and resolveApiUrl returns http://localhost:11434/v1 for ollama. Both exact.

One optional note. The variable is read first for every provider, not only those two, so setting it also points openai at a gateway. "for ollama and custom" is right about who needs it and narrower than who honours it, which is a fair trade for a table row. Mentioning it only so you know.

The localized READMEs carry no environment table, so nothing was owed there.

Merging shortly.