Enforce unique doc filenames and simple wiki-links (#109)

## Summary
- Rename section index files to match their titles (tutorials.md, reference.md, how-to.md, explanation.md) so all filenames are unique
- Convert all ~47 path-based wiki-links to simple filename format across 15 files
- Update doc-filenames task to no longer skip index.md files
- Update doc-links task to reject path-based links containing '/'

This ensures all wiki-links work correctly in obsidian.nvim by making links resolvable by filename alone.

## Testing
- `mise run doc-filenames` - all unique
- `mise run doc-links` - no broken or path-based links
- `mise run doc-titles` - no duplicates

Reviewed-on: https://forge.ops.eblu.me/eblume/blumeops/pulls/109

docs/reference/storage/backups.md

@@ -7,7 +7,7 @@ tags:
 
 # Backup Policy
 
-Daily automated backups from [[indri]] to [[sifaka | Sifaka]] NAS.
+Daily automated backups from [[indri]] to [[sifaka|Sifaka]] NAS.
 
 ## Schedule
 
@@ -30,8 +30,8 @@ Daily automated backups from [[indri]] to [[sifaka | Sifaka]] NAS.
 
 | Database | Host | Method |
 |----------|------|--------|
-| miniflux | [[postgresql | pg.ops.eblu.me]] | pg_dump stream |
-| teslamate | [[postgresql | pg.ops.eblu.me]] | pg_dump stream |
+| miniflux | [[postgresql|pg.ops.eblu.me]] | pg_dump stream |
+| teslamate | [[postgresql|pg.ops.eblu.me]] | pg_dump stream |
 
 ## Sifaka-Native Data
 
@@ -56,7 +56,7 @@ Some data lives directly on [[sifaka]] rather than being backed up to it (photos
 
 ## Backup Target
 
-Repository: `/Volumes/backups/borg/` on [[sifaka | Sifaka]]
+Repository: `/Volumes/backups/borg/` on [[sifaka|Sifaka]]
 
 ## Monitoring
 
@@ -70,5 +70,5 @@ Dashboard: "Borgmatic Backups" in [[grafana]]
 ## Related
 
 - [[borgmatic]] - Backup system details
-- [[sifaka | Sifaka]] - Backup storage
+- [[sifaka|Sifaka]] - Backup storage
 - [[postgresql]] - Database backups