feat(rebranding): Complete project rebranding

[matdev83]

feat(rebranding): Complete project rebranding

Scope: everything (docs, README, AGENTS, source code, package names, file names, comments, even LIP-specific HTTP headers).

We completely break any legacy/connections with LIP, LLM-Interactive-Proxy, Go-LIP and other legacy names, shortcuts and abbreviations tied to the original LIP.

From now on, this project becomes aiproxer, domain name for FQDN package naming aiproxer.com.

In the subsequent tasks to implement Open Core model we'll split further for the OSS core. This one specifically is named aiproxer where enterprise features will get released under the name aiproxer enterprise.

Conversion scheme:
github.com/matdev83/go-llm-interactive-proxy -> github.com/aiproxer/aiproxer
go-llm-interactive-proxy -> aiproxer
llm-interactive-proxy -> aiproxer
go lip -> aiproxer
golip -> aiproxer
go-lip -> aiproxer
*lip -> *aip (three-leter shortcut suffixes referring to the LIP)
lip* -> aip* (three-leter shortcut prefixes referring to the LIP)

Examples: lipstd package -> aipstd package. HTTP headers like X-LIP-something: become X-AIP-something: and so on.

Expected end state after this refactor: no LIP, Go-LIP, golip, llm-interactive-proxy and other legacy names/shortcuts mentions across the whole repo, including filenames, directory names, package names, help files, markdown files, tests. everywhere

Dependencies / sequencing

• No active hard prerequisite inside OSS Base; the implementation-ready staged SDD from spec: plan staged aiproxer complete rebranding #430 is the authoritative plan.
• Blocks feat(split): OSS / Enterprise split [ENDS OSS Base Milestone] ============================================ #398, the terminal OSS Base split gate.
• feat(performance): Add large-payload streaming fast path to avoid full request materialization #503/task: Implement Kiro spec large-payload-streaming-fast-path #532 are not hard prerequisites. Prefer avoiding unnecessary overlap with their high-churn request/runtime work where practical; whichever lands second must re-inventory current paths. This is coordination only.
• The production/package-ownership moves from pre-OSS core slimming have now landed through fix(feature): make generated plane policy canonical #591. task: Implement Kiro spec pre-oss-core-slimming #571 remains open only for final Kiro/repository closeout, so it is not a rebranding implementation blocker and no longer represents expected structural package churn. Rebranding must inventory the current post-fix(feature): make generated plane policy canonical #591 tree rather than historical pre-slimming paths.
• task: Implement Kiro spec bulk-inference-provider-expansion #545 provider expansion is independent; any renamed provider/profile package paths are a revalidation concern only.
• Treat all of the above as coordination guidance, not dependency edges.

[matdev83]

Status sync — implementation-ready rebranding SDD exists; rebrand not yet implemented

PR #430 merged the approved staged aiproxer-complete-rebranding Kiro SDD and its canonical spec.json is ready_for_implementation: true. The PR was explicitly spec-only and changed no production code.

#429 therefore remains open. The implementation phase should follow the staged migration plan in .kiro/specs/aiproxer-complete-rebranding/; the current repository still contains the legacy names/namespaces that this issue is intended to remove.