feat(cli): add local_smtp config

[7ttp]

TL;DR

adds local_smtp as the new preferred config key, keeps inbucket valid with a deprecation warning and updates the default template to use local_smtp

what's introduced:

local_smtp is now the preferred config/schema key, while existing
inbucket configs continue to work for now....

why

basically this moves the config away from an implementation specific name without breaking existing setups in phase 1 :)

ref

• closes Update old references to Inbucket with Mailpit #5222

[coveralls]

Coverage Report for CI Build 26726708757

Coverage decreased (-0.02%) to 63.779%

Details

• Coverage decreased (-0.02%) from the base build.
• Patch coverage: No coverable lines changed in this PR.
• 7 coverage regressions across 2 files.

Uncovered Changes

No uncovered changes found.

Coverage Regressions

7 previously-covered lines in 2 files lost coverage.

File	Lines Losing Coverage	Coverage
internal/utils/git.go	5	57.14%
internal/storage/rm/rm.go	2	80.61%

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Coverage Stats

Relevant Lines:	15759
Covered Lines:	10051
Line Coverage:	63.78%
Coverage Strength:	7.09 hits per line

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💛 - Coveralls