Fixes #1242

Describe the changes you have made in this PR -

Hoists `import json` from inside hot-path function bodies to module top in two services, matching the pattern from #1216 (which fixed #1209 for `copy` and `datetime` in `app/nodes/`). Same class of issue, different sites.

Files changed

• app/services/tracer_client/tracer_integrations.py — added `import json` at module top; removed it from inside two functions:
  • `get_all_integrations()` — the import was inside a `for` loop iterating integration records, re-running once per iteration
  • `get_grafana_credentials()` — per-call during integration resolution
• app/services/lambda_client.py — added `import json` at module top; removed it from inside `invoke_function()` (per Lambda invocation)

Diff summary

```
2 files changed, 2 insertions(+), 6 deletions(-)
```

Demo/Screenshot for feature changes and bug fixes -

```

Before — re-run on every call (loop case re-runs per iteration):

def get_all_integrations(self):
...
for integration in integrations:
if isinstance(creds, str):
import json # executes per integration record
integration["credentials"] = json.loads(creds)

After — imported once at module load:

import json # module top
...
def get_all_integrations(self):
...
for integration in integrations:
if isinstance(creds, str):
integration["credentials"] = json.loads(creds)
```

Local checks (clean baseline preserved):

```
$ make lint && make format-check && make typecheck && make test-cov
ruff check app/ tests/ -> All checks passed!
ruff format --check app/ tests/ -> 1057 files already formatted
mypy app/ -> Success: no issues found in 456 source files
pytest -> 4656 passed, 2 skipped, 21 warnings in ~49s
```

Code Understanding and AI Usage

Did you use AI assistance (ChatGPT, Claude, Copilot, etc.) to write any part of this code?

• No, I wrote all the code myself
• Yes, I used AI assistance (continue below)

If you used AI assistance:

• I have reviewed every single line of the AI-generated code
• I can explain the purpose and logic of each function/component I added
• I have tested edge cases and understand how the code handles them
• I have modified the AI output to follow this project's coding standards and conventions

Explain your implementation approach:

The change is the same surgical pattern as #1216: `import json` is moved out of the function body and added to the module's top-level imports, sorted alphabetically alongside the existing stdlib imports. Once `json` is in `sys.modules` after first import, the inside-function `import json` statement is not "free" — the interpreter still re-runs the import statement on every call, performing a `sys.modules` lookup and binding the name into the function's local namespace. The most egregious case here is `tracer_integrations.py:68`, where the original import sat inside a `for` loop iterating integration records, so the statement re-ran once per record.

No semantic change: `json.loads` and `json.JSONDecodeError` are referenced identically before and after; the only difference is where the name binding originates. The full test suite (4656 tests) continues to pass with the same skip count and no new warnings.

I considered also touching `app/nodes/resolve_integrations/node.py` (which has `import base64` and `import json` inside `_decode_org_id_from_token`) but kept it out of scope to keep this PR small and to avoid a function that was the subject of an unrelated, contentious prior PR — happy to send a follow-up if maintainers want it covered.

Checklist before requesting a review

• I have added proper PR title and linked to the issue
• I have performed a self-review of my code
• I can explain the purpose of every function, class, and logic block I added
• I understand why my changes work and have tested them thoroughly
• I have considered potential edge cases and how my code handles them
• If it is a core feature, I have added thorough tests (n/a — semantic-noop import hoist; existing suite covers these code paths)
• My code follows the project's style guidelines and conventions