feat(generative): add generative-meta support

[g-despot]

Closes #2158

Adds Configure.Generative.meta(...) and GenerativeConfig.meta(...) for the new generative-meta module, and returns its usage metadata. Follows the DigitalOcean addition (#2153); the protos already include GenerativeMeta, so no regen.

reasoning_effort gets its own MetaReasoningEffort literal because Meta accepts none and xhigh, which OpenAI's does not. Images are passed through, since the module supports them.

[orca-security-eu]

Orca Security Scan Summary

Status	Check	Issues by priority
Passed	Infrastructure as Code	0   0   0   0	View in Orca
Passed	SAST	0   0   0   0	View in Orca
Passed	Secrets	0   0   0   0	View in Orca
Passed	Vulnerabilities	0   0   0   0	View in Orca

[codecov-commenter]

Codecov Report

❌ Patch coverage is 87.27273% with 7 lines in your changes missing coverage. Please review.
✅ Project coverage is 88.73%. Comparing base (95b5d76) to head (c61bace).
⚠️ Report is 159 commits behind head on main.

Files with missing lines	Patch %	Lines
weaviate/collections/classes/generative.py	77.41%	7 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2162      +/-   ##
==========================================
+ Coverage   86.64%   88.73%   +2.09%     
==========================================
  Files         300      304       +4     
  Lines       23172    24007     +835     
==========================================
+ Hits        20077    21303    +1226     
+ Misses       3095     2704     -391     

☔ View full report in Codecov by Harness.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.