Relax fastapi upper bound (<0.116) — 7 months behind latest (0.128.0)

### Search before asking - [x] I have searched the Inference [issues](https://github.com/roboflow/inference/issues) and found no similar **open** bug report. ### Bug The `fastapi` dependency in `requirements/_requirements.txt` is pinned to `>=0.100,<0.116`: ``` fastapi>=0.100,<0.116 # be careful with upper pin - fastapi might remove support for on_event ``` FastAPI 0.116.0 was released on **2025-07-07** — over **7 months ago**. The latest FastAPI is **0.128.0** (2025-12-27). This means `inference` is incompatible with any project that requires a modern FastAPI version. ### Prior art This was partially addressed in #1398 / PR #1407 (merged 2025-07-10), which bumped the upper bound from `<0.111` to `<0.116`. However, FastAPI has since moved significantly further (0.116 → 0.128), and the same conflict pattern has re-emerged. ### Impact Any project that depends on both `inference` and a library requiring FastAPI ≥0.116 hits an unresolvable dependency conflict. For example, frameworks and shared libraries that track modern FastAPI versions force users to apply `[tool.uv] override-dependencies` workarounds to bypass the constraint — running `inference` against an untested FastAPI version anyway, but without upstream CI coverage. ### The `on_event` concern The pinned comment says: > be careful with upper pin - fastapi might remove support for on_event As of FastAPI 0.128.0, `on_event` is **deprecated but still functional** (replaced by `lifespan` handlers). It has not been removed. The concern that motivated the pin has not materialized in 12+ minor releases beyond the current upper bound. ### Suggested fix Bump the upper bound to cover current FastAPI releases, e.g.: ``` fastapi>=0.100,<0.129 ``` Or, ideally, migrate the `on_event` usage to `lifespan` handlers and remove the upper bound entirely. ### Environment - inference: 0.51.9 (also affects latest 0.64.6) - FastAPI latest: 0.128.0 - Python: 3.13 ### Minimal Reproducible Example ```bash uv init --bare --python 3.13 uv add inference "fastapi>=0.116" ``` Produces an unresolvable conflict: ``` Because inference>=0.51.9 depends on fastapi<0.116, and you require fastapi>=0.116: inference>=0.51.9 and fastapi>=0.116 are incompatible. ``` ### Are you willing to submit a PR? - [ ] Yes I'd like to help by submitting a PR!