timeline: remove GPU, add SSE status updates, DOCX export, single-file, engine-aware credits

- Remove GPU/cuttlefish engine from timeline.php, api/timeline.php, LegalTools.php, tools.js (all 4 langs)
- Add engine-aware credit cost: gpt-4o-mini=1 credit, gpt-4o=2 credits (matches redact pattern)
- Remove multiple attribute from file input (single document only)
- New api/timeline-stream.php: SSE endpoint emitting status events + final result
- New api/timeline-download.php: DOCX export of timeline events
- LegalTools::timeline() gains ?callable $onProgress for live status updates
- tools.js: spinner on run, SSE streaming fetch, Export to Word button
- Save to My Docs was already wired (showSaveResultButton at line 1136)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

includes/PricingCatalog.php

@@ -132,7 +132,7 @@ final class PricingCatalog
             'summarize' => 1,
             'translate' => 1,
             'korrespond_refine' => 1,
-            'timeline' => 2,
+            'timeline' => 1, // minimum (gpt-4o-mini); azure_full overrides to 2 in api/timeline.php
             'redact' => 1, // minimum (gpt-4o-mini); azure_full overrides to 2 in api/redact.php
             'barnevernet' => 3,
             'advocate' => 3,