fix: improve timeout.reconciliation error handling

[ragnarpa]

• Improve error handling of invalid input for timeout.reconciliation.
• Update docs for expected format of timeout.reconciliation.

Checklist:

• Either (a) I've created an enhancement proposal and discussed it with the community, (b) this is a bug fix, or (c) this does not need to be in the release notes.
• The title of the PR states what changed and the related issues number (used for the release note).
• I've included "Closes [ISSUE #]" or "Fixes [ISSUE #]" in the description to automatically close the associated issue.
• I've updated both the CLI and UI to expose my feature, or I plan to submit a second PR with them.
• Does this PR require documentation updates?
• I've updated documentation as required by this PR.
• Optional. My organization is added to USERS.md.
• I have signed off all my commits as required by DCO
• I have written unit and/or e2e tests for my change. PRs without these are unlikely to be merged.
• My build is green (troubleshooting builds).

[codecov]

Codecov Report

Merging #8964 (e4e5c88) into master (e9fae0d) will decrease coverage by 0.07%.
The diff coverage is 100.00%.

❗ Current head e4e5c88 differs from pull request most recent head f54ee8a. Consider uploading reports for the commit f54ee8a to get more accurate results

@@            Coverage Diff             @@
##           master    #8964      +/-   ##
==========================================
- Coverage   44.96%   44.88%   -0.08%     
==========================================
  Files         212      212              
  Lines       25264    25264              
==========================================
- Hits        11361    11341      -20     
- Misses      12296    12316      +20     
  Partials     1607     1607              

Impacted Files	Coverage Δ
util/env/env.go	90.90% <100.00%> (ø)
applicationset/services/scm_provider/github.go	57.64% <0.00%> (-23.53%)	⬇️

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[crenshaw-dev]

LGTM, thanks!