feat: reorganise bash scripts and add comprehensive documentation (#6)

## Summary

This PR completes the bash script restructuring and adds comprehensive documentation across all script categories.

### Bash Restructuring

- Moved cohort shell scripts (`remove_github_members.sh`, `update_github_teams.sh`) from `python/cohort/` into a new `bash/cohort/` directory
- Moved existing bash utilities (`add-keys-to-git.sh`, `fix-yubikey-perms.sh`, `list-yubikey-ssh-keys.sh`) into a new `bash/yubikey/` subdirectory
- Updated `run.sh` to support **Bash** as a third language option alongside TypeScript and Python
  - Bash scripts are run directly (no 1Password secret injection needed)
  - Category discovery and script listing works the same as for TS/Python
  - Removed dead "Root Scripts" logic that was no longer needed

### Documentation

Added `README.md` files for all script categories that were missing them:

- `bash/cohort/README.md` — cohort GitHub team management scripts
- `bash/yubikey/README.md` — YubiKey SSH key and permission utilities
- `typescript/src/crowdin/README.md` — Crowdin translation management scripts
- `typescript/src/discord/README.md` — Discord bot utility scripts
- `typescript/src/discourse/README.md` — Discourse forum management scripts
- `typescript/src/gitea/README.md` — Gitea bulk repository operation scripts
- `typescript/src/github/README.md` — GitHub API interaction scripts
- `typescript/src/music/README.md` — Music file metadata tools
- `typescript/src/s3/README.md` — S3-compatible object storage scripts
- `typescript/src/security/README.md` — Security analysis and reporting scripts
- `python/cohort/README.md` — Updated to remove moved shell scripts, fix usage commands

Also updated project-level docs:

- **`README.md`** — Corrected project structure, fixed running instructions (removed references to non-existent `make run-ts`/`make run-py` targets), added Bash prerequisites
- **`CLAUDE.md`** — Updated project overview, structure, development standards, and script-adding guides to reflect the current state of the project

✨ This PR was created with help from Hikari~ 🌸

Co-authored-by: Naomi Carrigan <commits@nhcarrigan.com>
Reviewed-on: #6
Co-authored-by: Hikari <hikari@nhcarrigan.com>
Co-committed-by: Hikari <hikari@nhcarrigan.com>

bash/yubikey/list-yubikey-ssh-keys.sh

@@ -0,0 +1,22 @@
+#!/bin/bash
+echo "Scanning YubiKey slots for SSH keys..."
+echo "---------------------------------------------------"
+
+# Loop through the slots that support SSH keys
+for SLOT in 9a 9c 9d 9e; do
+    # Try to export the key to a temp file
+    if ykman piv keys export $SLOT /tmp/yubi_tmp.pem > /dev/null 2>&1; then
+        echo -e "\033[0;32mFOUND KEY IN SLOT $SLOT:\033[0m"
+        
+        # Check if there is a certificate label
+        LABEL=$(ykman piv certificates export $SLOT - 2>/dev/null | openssl x509 -noout -subject 2>/dev/null)
+        if [ ! -z "$LABEL" ]; then
+            echo "Certificate Label: $LABEL"
+        fi
+
+        # Convert to SSH format and print
+        ssh-keygen -i -m PKCS8 -f /tmp/yubi_tmp.pem
+        echo "---------------------------------------------------"
+        rm /tmp/yubi_tmp.pem
+    fi
+done