chore(branding) added branding, best practice to repo

CONTRIBUTING.md

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+# Contributing
+
+Thanks for taking the time. This is an unofficial Proton Drive client that people trust with real
+files, so the bar for changes that touch the filesystem, the sync engine, or the database is
+deliberately high — everything else is ordinary Rust review.
+
+## Before you start
+
+- Read [`AGENTS.md`](AGENTS.md) for repository conventions and
+  [`docs/ARCHITECTURE.md`](docs/ARCHITECTURE.md) for how the daemon, front ends, and SDK fit
+  together.
+- Check [`docs/BUGS.md`](docs/BUGS.md) — it is the authoritative issue ledger, and your problem may
+  already be tracked there with context.
+- For anything larger than a fix, open an issue first so the design can be discussed before you
+  spend the time.
+
+## Development setup
+
+```bash
+git clone https://github.com/narrrl/proton-drive-linux.git
+cd proton-drive-linux
+cargo build --workspace
+```
+
+GUI and FUSE targets need the GTK4, libadwaita, WebKitGTK 6, libsecret, D-Bus, and FUSE3
+development packages listed in the [README](README.md#prerequisites). Minimum supported Rust
+version is 1.96.
+
+## Quality gates
+
+CI runs exactly these, and they must pass with zero warnings:
+
+```bash
+cargo fmt --all -- --check
+cargo clippy --workspace --all-targets -- -D warnings
+cargo test --workspace --locked
+scripts/fuse-acceptance.sh --offline-only
+```
+
+Changes to the FUSE layer, sync, or the pending-operation queue should also be exercised against a
+real mount before review — see [`docs/TESTING.md`](docs/TESTING.md). Live runs are destructive:
+use a dedicated test account, never one holding data you cannot lose.
+
+## Making changes
+
+- **Keep shared logic in `pdfs-core`.** The CLI and GUI never touch the database or the network;
+  they speak the control protocol to the daemon.
+- **The SQLite schema is forward-only.** Never edit a shipped migration — add a new one and bump
+  `SCHEMA_VERSION` in `crates/pdfs-core/src/db/migrations.rs`.
+- **Typed errors and `?` over panics** on runtime paths. Blocking filesystem, keyring, or
+  control-socket work stays off GTK's main thread.
+- **`staging/` and `recovery/` may hold the only copy of user data.** Nothing may clear or purge
+  them opportunistically.
+
+## Commits and pull requests
+
+Commits follow scoped [Conventional Commits](https://www.conventionalcommits.org), e.g.
+`fix(fuse,core): keep truncate composable with queued revisions`.
+
+A pull request should state:
+
+- the user-visible effect and which crates it touches,
+- the `docs/BUGS.md` entries it fixes or affects,
+- the commands you ran to verify it,
+- screenshots for GTK changes,
+- and, explicitly, any migration, recovery, data-loss, or packaging implications.
+
+## Security
+
+Do not open a public issue for a vulnerability — see [SECURITY.md](SECURITY.md).