feature: add mkdocs-material documentation site with CI deployment

Generate comprehensive documentation for all 173 source units and
integrate mkdocs-material into the build toolchain. Documentation
covers kernel core, x86 architecture, drivers, applications, and
all subsystems with a tabbed navigation structure.

- Add mkdocs.yml with material theme, mermaid support, and tabbed nav
- Add doc/index.md landing page
- Generate doc/src/ markdown for every Pascal unit in src/
- Reorganize planning docs into doc/planning/
- Add compat, lvglh, and toolchain doc sections
- Update Dockerfile to install python3 and mkdocs-material (pinned <2)
- Replace pasdoc-based compile_docs.sh with mkdocs build --strict
- Add compile_docs.sh to the main build pipeline in compile.sh
- Add deploy-docs step in .drone.yml with host volume mount to nginx
- Add site/.gitkeep for build output directory

doc/src/core/enc/core.enc.fnv1a.md

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+# core.enc.fnv1a
+
+FNV-1a (Fowler-Noll-Vo) non-cryptographic hash in 32-bit and 64-bit widths.
+
+## Overview
+
+`core.enc.fnv1a` implements the FNV-1a variant of the Fowler-Noll-Vo hash algorithm. FNV-1a XORs each input byte into the hash value before multiplying by the FNV prime, which provides better avalanche characteristics than the original FNV-1 (which multiplies first). The algorithm is simple, fast, and produces well-distributed hashes suitable for hash tables, Bloom filters, and checksums.
+
+FNV-1a is the primary hash function used by `core.ds.hashmap` (key hashing) and `core.ds.bloom` (first of two hash functions in the double-hashing scheme).
+
+## Dependencies
+
+- `io.syslog` — test output (implementation only)
+- `memory.heap` — `kfree` (implementation only)
+- `core.strings` — test output formatting (implementation only)
+
+## Functions and Procedures
+
+### Hash_FNV1a32
+```pascal
+function Hash_FNV1a32(Data : void; DataLen : uint32) : uint32;
+```
+Computes a 32-bit FNV-1a hash of `DataLen` bytes starting at `Data`.
+- Initial basis: `$811C9DC5`
+- FNV prime: `$01000193`
+- Per byte: `h = (h xor byte) * prime`
+
+Zero-length input returns the basis value `$811C9DC5`.
+
+### Hash_FNV1a64
+```pascal
+function Hash_FNV1a64(Data : void; DataLen : uint32) : uint64;
+```
+Computes a 64-bit FNV-1a hash.
+- Initial basis: `$CBF29CE484222325`
+- FNV prime: `$00000100000001B3`
+
+Zero-length input returns the basis value.
+
+### UnitTest
+```pascal
+procedure UnitTest;
+```
+Runs the FNV-1a test suite (known basis for empty input, determinism, distinctness for different inputs, length sensitivity, independence of 32-bit and 64-bit variants) and logs a pass/fail summary to syslog under the `'FNV1A'` channel.
+
+## Notes
+
+Both functions are purely computational with no side effects or allocations. They may be called from any context.
+
+The low 32 bits of `Hash_FNV1a64` are not guaranteed to equal `Hash_FNV1a32` for the same input; they are independent algorithms.