Establish Faceplate repository baseline

[barfle]

Summary

Establishes Faceplate as a neutral, appliance-focused downstream of kmscon while preserving the upstream history.

• defines the Faceplate identity and upstream synchronization policy
• records upstream and bundled third-party attribution
• keeps Dataplicity branding out of the core binary and repository
• adds contribution, security, ownership, and pull-request policies
• replaces the inherited workflow with pinned GCC/Clang, minimal-backend, and format checks
• retains the repository's existing GitHub CodeQL default setup
• adds Dependabot configuration
• documents the required main and release/* branch rulesets

Branding decision

The core remains vendor-neutral. A Dataplicity-branded build must consume separately licensed runtime theme assets at image-build time; the logo must not be compiled into Faceplate.

Validation

• transferred main matches upstream commit 791e659f2420e00cda7c39b4eb53f3c2844b4885
• YAML parses successfully
• git diff --check
• meson format --recursive --check-only
• GCC build and tests
• Clang build and tests
• minimal framebuffer/PSF build and tests

Follow-up after merge

Apply the documented GitHub rulesets to main and release/*, require the named CI checks plus GitHub's default CodeQL check, enable automatic branch updates, and use squash merges.