feat(web): v0.1 UI — calendar heatmap, day detail, trade detail

[SwathiMystery]

What

First web UI for khata. FastAPI + Jinja2 + HTMX. No client JS framework. Single stylesheet with dark mode via prefers-color-scheme. Logo-matched amber/indigo palette.

Pages

route	purpose
GET /	redirect to the current month's calendar
GET /calendar/{year}/{month}	month grid, P&L-coloured days, Tue/Thu expiry markers, month-level totals, prev/next nav
GET /day/{YYYY-MM-DD}	trade table, summary strip (trades/wins/losses/fees), inline daily reflection editor
GET /trade/{id}	trade meta, executions/fills table, tag chips with add/remove, note editor

HTMX partials

route	purpose
POST /notes/trade/{id}	save trade note on blur, returns updated note block
POST /notes/day/{YYYY-MM-DD}	save daily note on blur
POST /tags/trade/{id}	add tag (kind: psych/setup/mistake/custom), returns tag list
DELETE /tags/trade/{id}/{tag}	remove tag, returns tag list

CLI

khata web                                # 127.0.0.1:8000, reload on
khata web --host 0.0.0.0 --port 9000     # LAN-reachable
khata web --no-reload                    # production/container

Tests

12 new smoke tests via fastapi.testclient.TestClient. Covers every route, every HTMX round-trip, and edge cases (invalid date, missing trade, empty day). Full suite: 34/34 green.

Notes

• Schema untouched. Reads-only against existing tables (trades, executions, trade_legs, notes, tags, trade_tags).
• HTMX via unpkg CDN — comment in base.html documents vendoring option for air-gapped installs.
• FastAPI's Depends() idiom trips ruff's B008 on import-time function calls. Added a per-file ignore only for khata/web/main.py — doesn't affect the rest of the codebase.
• datetime.utcnow() replaced with timezone-aware equivalent for Python 3.12+ deprecation.

Verification

Ran against a live Dhan account (103 executions, 18 trades from my real sync):

• Calendar shows the month with wins/losses correctly coloured, Tue/Thu expiry dots visible
• Day view lists each trade with IST time, entry/exit, direction badge, links to trade detail
• Trade detail shows avg entry/exit, fees, duration; daily note + tag add persists across refresh
• HTMX round-trips completed in ~5ms per op

Checklist

• 12 new tests, all green (34 total)
• uv run ruff check khata tests clean (with scoped B008 allowance)
• uv run ruff format khata tests applied
• Docs: CLI help is self-documenting; ROADMAP.md v0.1 scope matches
• No schema change