Task: Fix provider baseUrl stripping endpoint suffixes before /models
## Problem
When users entered a full endpoint URL as the provider base URL (e.g.
`https://api.openai.com/v1/chat/completions` instead of
`https://api.openai.com/v1`), the server would append `/models` to it,
producing the invalid path `/v1/chat/completions/models` — resulting in
HTTP 404 errors for model discovery, connection tests, and analysis.
## Changes
### `artifacts/api-server/src/lib/aiAnalysis.ts`
- Added exported `normalizeBaseUrl(raw: string): string` helper that:
- Strips trailing slashes
- Strips known endpoint suffixes: `/chat/completions`, `/completions`, `/messages`
- Strips trailing slashes again after suffix removal
- Applied `normalizeBaseUrl` in `callOpenAiCompatible`, `callAnthropic`,
and `listProviderModels` (replacing the previous bare `.replace(/\/$/, "")`)
### `artifacts/api-server/src/routes/providers.ts`
- Imported `normalizeBaseUrl` from aiAnalysis
- Applied normalization to `baseUrl` in the POST /providers (create) handler
- Applied normalization to `baseUrl` in the PATCH /providers/:id (update) handler
- This ensures the canonical normalized value is persisted from the start
### `artifacts/api-server/src/routes/providers.listModels.test.ts`
- Added import of `normalizeBaseUrl`
- Added a new `describe("normalizeBaseUrl")` block with 7 unit tests covering:
all three suffix patterns, trailing slashes, clean URLs, combined suffix+slash,
and non-matching partial suffixes
## Test results
All 13 tests pass (6 existing + 7 new normalization unit tests).
Replit-Task-Id: 9ab5c336-d54e-4bc3-8f01-0b7486365c4b
9648b8553c