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>

python/cohort/analyse_availability.py

@@ -1,6 +1,26 @@
+"""Analyse applicant availability from a markdown table and produce UTC block stats.
+
+Reads a markdown table of availability responses and a Discord verification file,
+then produces a JSON summary of coverage across morning/afternoon/evening UTC blocks
+for each day of the week.
+
+Data files (place in data/):
+  - table.md                   Markdown table of applicant availability responses
+  - discord_verification.json  Discord ID verification results (from verify_discord.py)
+
+Outputs (written to data/):
+  - availability_analysis.json  UTC block distribution per applicant
+
+Env vars:
+  - None
+"""
+
 import json
 import re
 from collections import defaultdict
+from pathlib import Path
+
+DATA_DIR = Path(__file__).parent.parent.parent / "data"
 
 DAYS = ["Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday", "Sunday"]
 
@@ -99,7 +119,7 @@ def analyze_applicant_availability(timezone_str: str, day_slots: dict) -> dict:
 
 def parse_table_md() -> list[dict]:
     """Parse table.md and extract availability data"""
-    with open("table.md") as f:
+    with open(DATA_DIR / "table.md") as f:
         content = f.read()
 
     lines = content.strip().split("\n")
@@ -131,7 +151,7 @@ def parse_table_md() -> list[dict]:
 
 
 def main():
-    with open("discord_verification.json") as f:
+    with open(DATA_DIR / "discord_verification.json") as f:
         verification = json.load(f)
 
     verified_ids = {v[0] for v in verification["verified"]}
@@ -167,7 +187,7 @@ def main():
             }
         )
 
-    with open("availability_analysis.json", "w") as f:
+    with open(DATA_DIR / "availability_analysis.json", "w") as f:
         json.dump(availability_results, f, indent=2)
 
     block_distribution = defaultdict(int)