Fix re-embedding issues and improve retry strategy (#515)

* fix: filter empty content in rebuild embeddings queries

Update collect_items_for_rebuild() to properly filter out items with
empty or whitespace-only content before submitting embedding jobs.

Changes:
- Sources: add string::trim(full_text) != '' filter
- Notes: add string::trim(content) != '' filter
- Insights: add content != none AND string::trim(content) != '' filter
  (previously had no content filter at all)

This prevents unnecessary job submissions that would fail validation
in the individual embed commands.

Ref #513

* feat: add command_id to embedding error logs

Add get_command_id() helper to extract command_id from execution context.
Include command_id in error logs for all embedding commands:
- embed_note_command
- embed_insight_command
- embed_source_command
- create_insight_command

This makes it easier to trace failed embedding jobs back to specific
command records in the database.

Ref #513

* fix: improve logging for embedding commands

Log improvements:
- Add command_id to all embedding error logs for traceability
- Transaction conflicts in repo_insert now log at DEBUG (not ERROR)
- Embedding API errors log at DEBUG, only ERROR when retries exhausted
- Friendlier retry messages: "This will be retried automatically"
- Include model name and command_id in generate_embeddings errors

Files changed:
- commands/embedding_commands.py: command_id in logs, friendlier messages
- open_notebook/database/repository.py: DEBUG for transaction conflicts
- open_notebook/utils/embedding.py: DEBUG logging, pass-through command_id

Ref #513

* fix: correct field names in rebuild embeddings status endpoint

The API status endpoint was looking for wrong field names:
- sources_processed → sources_submitted
- notes_processed → notes_submitted
- insights_processed → insights_submitted
- processed_items → jobs_submitted
- failed_items → failed_submissions

The command outputs "_submitted" because embedding happens async
(we count jobs submitted, not items processed).

Ref #513

* fix: update rebuild UI text to reflect async job submission

Changed terminology from "Completed/processed" to "Jobs Submitted"
since the rebuild command submits embedding jobs for async processing,
not completing them synchronously.

Updated in all locales: en-US, pt-BR, zh-CN, zh-TW, ja-JP

Ref #513

* refactor: migrate retry strategy from allowlist to blocklist

- Change from `retry_on: [RuntimeError, ...]` to `stop_on: [ValueError]`
- This is more resilient: new exception types auto-retry by default
- Simplified exception handling: ValueError = permanent, else = retry
- Transient errors logged at DEBUG (surreal-commands logs final failure)
- Permanent errors (ValueError) logged at ERROR

Ref #513

open_notebook/database/repository.py

@@ -180,7 +180,12 @@ async def repo_insert(
     except RuntimeError as e:
         if ignore_duplicates and "already contains" in str(e):
             return []
-        logger.error(str(e))
+        # Log transaction conflicts at debug level (they are expected during concurrent operations)
+        error_str = str(e).lower()
+        if "transaction" in error_str or "conflict" in error_str:
+            logger.debug(str(e))
+        else:
+            logger.error(str(e))
         raise
     except Exception as e:
         if ignore_duplicates and "already contains" in str(e):